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PubMed2004

Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia.

BACKGROUND: Cluster sample study designs are cost effective, however cluster samples violate the simple random sample assumption of independence of observations. Failure to account for the intra-cluster correlation of observations when sampling through clusters may lead to an under-powered study. Researchers therefore need estimates of intra-cluster correlation for a range of outcomes to calculate sample size. We report intra-cluster correlation coefficients observed within a large-scale cross-sectional study of general practice in Australia, where the general practitioner (GP) was the primary sampling unit and the patient encounter was the unit of inference. METHODS: Each year the Bettering the Evaluation and Care of Health (BEACH) study recruits a random sample of approximately 1,000 GPs across Australia. Each GP completes details of 100 consecutive patient encounters. Intra-cluster correlation coefficients were estimated for patient demographics, morbidity managed and treatments received. Intra-cluster correlation coefficients were estimated for descriptive outcomes and for associations between outcomes and predictors and were compared across two independent samples of GPs drawn three years apart. RESULTS: Between April 1999 and March 2000, a random sample of 1,047 Australian general practitioners recorded details of 104,700 patient encounters. Intra-cluster correlation coefficients for patient demographics ranged from 0.055 for patient sex to 0.451 for language spoken at home. Intra-cluster correlations for morbidity variables ranged from 0.005 for the management of eye problems to 0.059 for management of psychological problems. Intra-cluster correlation for the association between two variables was smaller than the descriptive intra-cluster correlation of each variable. When compared with the April 2002 to March 2003 sample (1,008 GPs) the estimated intra-cluster correlation coefficients were found to be consistent across samples. CONCLUSIONS: The demonstrated precision and reliability of the estimated intra-cluster correlations indicate that these coefficients will be useful for calculating sample sizes in future general practice surveys that use the GP as the primary sampling unit.

Australia↗

PubMed2005

Human auditory cortical processing of changes in interaural correlation.

Sensitivity to the similarity of the acoustic waveforms at the two ears, and specifically to changes in similarity, is crucial to auditory scene analysis and extraction of objects from background. Here, we use the high temporal resolution of magnetoencephalography to investigate the dynamics of cortical processing of changes in interaural correlation, a measure of interaural similarity, and compare them with behavior. Stimuli are interaurally correlated or uncorrelated wideband noise, immediately followed by the same noise with intermediate degrees of interaural correlation. Behaviorally, listeners' sensitivity to changes in interaural correlation is asymmetrical. Listeners are faster and better at detecting transitions from correlated noise than transitions from uncorrelated noise. The cortical response to the change in correlation is characterized by an activation sequence starting from approximately 50 ms after change. The strength of this response parallels behavioral performance: auditory cortical mechanisms are much less sensitive to transitions from uncorrelated noise than from correlated noise. In each case, sensitivity increases with interaural correlation difference. Brain responses to transitions from uncorrelated noise lag those from correlated noise by approximately 80 ms, which may be the neural correlate of the observed behavioral response time differences. Importantly, we demonstrate differences in location and time course of neural processing: transitions from correlated noise are processed by a distinct neural population, and with greater speed, than transitions from uncorrelated noise.

Acoustic Stimulation↗

PubMed2006

Correlation of relative permeability and relative cerebral blood volume in high-grade cerebral neoplasms.

OBJECTIVE: The purpose of this study was to correlate the degree of contrast enhancement on dynamic contrast-enhanced T1-weighted MRI and the relative cerebral blood volume (rCBV) values on T2*-weighted MRI in patients with high-grade brain neoplasms. SUBJECTS AND METHODS: Ten patients with biopsy-proven high-grade gliomas underwent dynamic contrast-enhanced MRI using T1-weighted fast spoiled gradient-echo technique (TR/TE, 8.3/1.5) during i.v. infusion of 0.1 mmol/kg of MR contrast medium. This sequence was followed within 5 minutes by dynamic susceptibility contrast (DSC) imaging (1,500/80) during i.v. infusion of 0.2 mmol/kg of MR contrast medium. Dynamic contrast-enhanced analysis was performed using the maximum-signal-intensity algorithm, and DSC analysis was performed using the negative enhancement integral program. For each tumor, we performed two comparisons: first, the average dynamic contrast-enhanced and rCBV values within a region of interest drawn around the entire contrast-enhancing tumor on a single image through the center of the lesion and, second, the highest dynamic contrast-enhanced and highest rCBV values within each tumor. Statistical analyses of the first comparison were performed using Pearson's correlation coefficient, R2 correlation coefficient, and Spearman's rank correlation and for the second comparison using Kendall's tau correlation. RESULTS: The mean signal intensity values ranged between 3.48 and 7.16 SDs above baseline values (mean, 4.89 SDs). The mean rCBV values ranged between 57.9% and 122.7% of the normal lentiform nucleus (mean, 76.6%). The Pearson's correlation coefficient was 0.867, the R2 correlation coefficient was 0.752, and the Spearman's rank correlation was 0.794 (p = 0.001). Dynamic contrast-enhanced values from the region of highest signal intensity ranged between 7.7 and 48.6 SDs above baseline values (mean, 17.3 SDs). The highest rCBV values ranged between 105% and 400% of the normal lentiform nucleus (mean, 292%). The correlation was estimated to be 0.7778 and was statistically significant at the 0.01 level of statistical significance (p = 0.0035). CONCLUSION: We found a high correlation between degree of contrast enhancement on dynamic contrast-enhanced images and rCBV values in whole tumors and in regions having the highest degree of contrast enhancement in this small study. Our findings, which suggest that relative permeability and rCBV values may be correlated in high-grade glial neoplasms, deserve further study in a larger patient population.

Adult↗

PubMed1993

Lack of correlation between site of wrist pain and location of noncommunicating defects shown by three-compartment wrist arthrography.

OBJECTIVE: Communicating defects shown by wrist arthrography often correlate poorly with the location of the patient's symptom(s). No study of wrist arthrography in which noncommunicating defects have been isolated, described, and correlated with the site of patients' symptoms has been reported. The aim of this study was to correlate the site(s) of patients' pain and the location(s) of noncommunicating defects shown by wrist arthrography. MATERIALS AND METHODS: One hundred noncommunicating capsular defects and incomplete defects of the interosseous ligaments and triangular fibrocartilage in 82 patients were identified from 462 three-compartment wrist arthrograms. Correlation between the sites of pain and sites of the noncommunicating defect was described as: (1) exact correlation, (2) ulnar/radial side correlation, (3) ambiguous correlation, or (4) no correlation. Statistical analysis was performed for each type of defect separately, in aggregate for patients who had more than one defect, and by separate analysis using patients' age (less than or greater than 30 years old). RESULTS: Capsular defects were detected in 65 patients, incomplete perforations of the triangular fibrocartilage in 28 patients, and incomplete defects of the scapholunate and lunotriquetral ligament in three patients each. No statistically significant correlation was found between individual defects and symptoms or between the site(s) of symptoms and patterns of multiple noncommunicating defects. Further, age did not influence the degree of correlations (chi 2 = 0.000-0.476, p values = 0.49-1.00). CONCLUSION: Attribution of patient's symptoms to noncommunicating defects shown by wrist arthrography is not reliable. Cases in which site-specific arthrographic defects directly correlate may be fortuitous. Additional studies will be necessary to determine the future role of wrist arthrography in the evaluation of the painful wrist.

Adult↗

PubMed2005

Expression of vascular endothelial growth factor in hepatocellular carcinoma and the surrounding liver and correlation with MRI findings.

OBJECTIVE: The purpose of our study was to assess the correlation between the quantitative and qualitative imaging findings on unenhanced and gadolinium-enhanced MR images and the intensity of vascular endothelial growth factor (VEGF) expression in hepatocellular carcinomas and in the surrounding nontumorous liver. MATERIALS AND METHODS: The intensities of VEGF expression in hepatocellular carcinoma and in the surrounding liver by Western blot analysis were converted to VEGF expression indexes (VEGF(IND)) in 22 surgical specimens ranging in size from 14 to 126 mm (mean, 47.6 +/- 29.5 mm) that were resected in 22 patients (17 men and five women; age range, 41-85 years [mean, 64 years]) between April 2000 and October 2002. MR images were retrospectively evaluated to determine contrast-to-noise ratios (CNRs), signal intensity SD ratios, and phase-shift indexes. Signal intensity characteristics of hepatocellular carcinomas were reviewed independently by two experienced radiologists who were unaware of the pathologic diagnosis or the results of immunoblotting. CNRs, SD ratios, and phase-shift indexes were correlated with VEGF(IND) using a simple regression test, and signal intensity characteristics were correlated with VEGF(IND) using the Spearman's rank correlation test. RESULTS: On opposed-phase T1-weighted spoiled gradient-recalled echo (GRE) images, CNRs correlated inversely with the VEGF(IND) of hepatocellular carcinomas (r = -0.46, p = 0.038). CNRs on T2-weighted fast spin-echo images correlated directly with the VEGF(IND) of hepatocellular carcinomas (r = 0.49, p = 0.025), and on gadolinium-enhanced hepatic arterial phase GRE images marginally and inversely correlated with VEGF(IND) (r = -0.39, p = 0.081). On T2-weighted fast spin-echo images, SD ratios correlated directly with the VEGF(IND) of hepatocellular carcinomas (r = 0.44, p = 0.044). No correlation was found between phase-shift indexes and VEGF expression. The qualitatively assessed signal intensity heterogeneities of hepatocellular carcinomas correlated directly with the VEGF(IND) of hepatocellular carcinomas on opposed-phase T1-weighted GRE, T2-weighted fast spin-echo, hepatic arterial phase GRE, and equilibrium phase GRE images. CONCLUSION: Our results indicate that the signal intensity and heterogeneity of hepatocellular carcinomas on MR images correlate with the degree of VEGF expression in hepatocellular carcinomas.

Adult↗

PubMed2006

Exploration of statistical dependence between illness parameters using the entropy correlation coefficient.

UNLABELLED: The entropy correlation coefficient (ECC) is a useful tool for measuring statistical dependence between variables. We employed this tool to search for pairs of variables that correlated in the chronic fatigue syndrome (CFS) Computational Challenge dataset. Highly related variables are candidates for data reduction, and novel relationships could lead to hypotheses regarding the pathogenesis of CFS. METHODS: Data for 130 female participants in the Wichita (KS, USA) clinical study [1] was coded into numerical values. Metric data was grouped using Gaussian mixture models; the number of groups was chosen using Bayesian information content. The pair-wise correlation between all variables was computed using the ECC. Significance was estimated from 1000 iterations of a permutation test and a threshold of 0.01 was used to identify significantly correlated variables. RESULTS: The five dimensions of multidimensional fatigue inventory (MFI) were all highly correlated with each other. Seven Short Form (SF)-36 measures, four CFS case-defining symptoms and the Zung self-rating depression scale all correlated with all MFI dimensions. No physiological variables correlate with more than one MFI dimension. MFI, SF-36, CDC symptom inventory, the Zung self-rating depression scale and three Cambridge Neuropsychological Test Automated Battery (CANTAB) measures are highly correlated with CFS disease status. DISCUSSION: Correlations between the five dimensions of MFI are expected since they are measured from the same instrument. The relationship between MFI and Zung depression index has been previously reported. MFI, SF-36, and Centers for Disease Control and Prevention (CDC) symptom inventory are used to classify CFS; it is not surprising that they are correlated with disease status. Only one of the three CANTAB measures that correlate with disease status has been previously found, indicating the ECC identifies relationships not found with other statistical tools. CONCLUSION: The ECC is a useful tool for measuring statistical dependence between variables in clinical and laboratory datasets. The ECC needs to be further studied to gain a better understanding of its meaning for clinical data.

Adult↗

PubMed2004

[Correlation between uptake of 99Tcm-MIBI and expression of multidrug resistant protein in breast cancer].

OBJECTIVE: To assess the correlation between uptake of (99)Tc(m)-MIBI and expression level of multidrug resistant protein in breast cancer. METHODS: Thirty pathologically confirmed patients with primary invasive ductal carcinoma were examined by (99)Tc(m)-MIBI scintigraphy at 15 min and 90 min after injecting the tracer. The uptake of (99)Tc(m)-MIBI at the region of interest (ROI) was evaluated as tumor to normal background (T/N) ratio. Retention index (RI) was calculated from the early uptake ratio (EUR) and updelayed take ratio (DUR). The expression of P-glycoprotein (P-gp) and multidrug resistant-associated protein (MRP) was detected by immunohistochemistry and the results were expressed as optical density (A). The data were analyzed by t test, Pearson correlation and partial correlation analysis. RESULTS: The expression of P-gp and MRP in tumor tissue was 0.1183 +/- 0.0700 and 0.1195 +/- 0.0522, respectively. In group with RI < 0. the expression of P-gp and MRP was 0.2181 +/- 0.0384 and 0.1718 +/- 0.0479, respectively. In group with RI >/= 0, the expression of P-gp and MRP was 0.1057 +/- 0.0217 and 0.0967 +/- 0.0362, respectively. There were significant differences between the two groups (t = 6.61, P = 0.0001; t = 5.01, P = 0.002). There was positive correlation between P-gp and RI (r = -0.919, P = 0.001), DUR (r = -0.675, P = 0.001), MRP(r = 0.549, P = 0.001), respectively, but no correlation between P-gp and EUR (r = -0.097, P = 0.610). There was positive correlation between MRP and RI (r = -0.547, P = 0.002), but no correlation between MRP and EUR (r = 0.292, P = 0.117) or DUR (r = -0.173, P = 0.361). Partial correlation analysis showed that there was high positive correlation between P-gp and RI (r = -0.8847, P = 0.001), but no significant correlation between MRP and RI (r = -0.1296, P = 0.512). CONCLUSION: The study suggests that increased level of P-gp expression may contribute to a low accumulation of (99)Tc(m)-MIBI in breast cancer, but no correlation with the expression level of MRP. Thus (99)Tc(m)-MIBI scintigraphy may predict the MDR development associated with P-gp expression in breast carcinoma.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

A general class of correlation coefficients for the 2 x 2 crossover design.

The Pearson correlation coefficient and the Kendall correlation coefficient are two popular statistics for assessing the correlation between two variables in a bivariate sample. We indicate how both of these statistics are special cases of a general class of correlation statistics that is parameterized by gamma element of [0, 1]. The Pearson correlation coefficient is characterized by gamma = 1 and the Kendall correlation coefficient by gamma = 0, so they yield the upper and lower extremes of the class, respectively. The correlation coefficient characterized by gamma = 0.5 is of special interest because it only requires that first-order moments exist for the underlying bivariate distribution, whereas the Pearson correlation coefficient requires that second-order moments exist. We derive the asymptotic theory for the general class of sample correlation coefficients and then describe the use of this class of correlation statistics within the 2 x 2 crossover design. We illustrate the methodology using data from the CLIC trial of the Childhood Asthma Research and Education (CARE) Network.

Adolescent↗

PubMed1995

Echocardiographic assessment of systolic and diastolic left ventricular function using an automatic boundary detection system. Correlation with established invasive and non invasive parameters.

Systolic and diastolic left ventricular function was assessed using an echocardiographic automatic boundary detection system (ABD) in 50 unselected patients undergoing left cardiac catheterisation. Automatic boundary detection system derived parameters (fractional area change [FAC], peak positive rate of area change [+dA/dt] and peak negative rate of area change [-dA/dt]) were compared with invasively (left ventricular angiography and pressures) and non invasively (Doppler mitral filling velocities and isovolumic relaxation time) acquired conventional indices of ventricular function. Adequate detection of endocardial boundaries and subsequent measurements using the ABD system were achieved in 40/50 (80%) patients in the short axis parasternal view, in 41/50 (82%) in the apical four chamber view and in 34/50 (68%) in both views. For the whole group of patients the FAC (maximal left ventricular diastolic area--minimal left ventricular systolic area/maximal left ventricular diastolic area) estimated in the short axis view correlated with the angiographic ejection fraction (EF) measured in the right oblique projection (r = 0.51, p < 0.001). There was only a weak correlation of the FAC estimated in the apical four chamber view with the EF (r = 0.36, p < 0.01). The mean FAC (mean value of the FAC in the short axis and apical four chamber views) correlated reasonably with the EF (r = 0.62, p < 0.0001). There was no correlation between ABD derived parameters and left ventricular end diastolic pressure (LVEDP) in these patients. In a subgroup of patients with normal coronary arteries and left ventricular function (n = 17), although there was no correlation between EF and FAC, there was a strong positive correlation between FAC (apical four chamber and mean) and LVEDP (r = 0.77, p < 0.01 and r = 0.87, p < 0.01 respectively). No correlation was found in these patients between EF and LVEDP. In a further subgroup of patients with angiographically abnormal left ventricular function (EF < 45%), there was a positive correlation between FAC (short axis, apical four chamber and mean) and EF (r = 0.52, p < 0.05, r = 0.83, p < 0.0001 and r = 0.80, p < 0.001 respectively) and a negative correlation between FAC (short axis and mean) and LVEDP (r = -0.52, p < 0.05 and r = -0.60, p < 0.01 respectively). There was also a negative correlation between LVEDP and EF in the same subgroup of patients (r = -0.65, p < 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed2003

C677T single nucleotide polymorphisms of the human methylene tetrahydrofolate reductase and specific identification : a novel strategy using two-color cross-correlation fluorescence spectroscopy.

BACKGROUND: A methylene tetrahydrofolate reductase (MTHFR) deficiency at site C677T renders the enzyme thermolabile and consequently represents a risk factor for vascular disease, neural tube defects, preeclampsia, and thrombosis. Highly specific identification techniques for genotyping are mandatory to give guidance for the diagnosis and monitoring of this deficiency. METHODS: A new approach for performing genotyping has been introduced with the identification of single nucleotide polymorphisms of the human MTHFR. It is based on PCR followed by two-color cross-correlation fluorescence spectroscopy (FCS). Experiments were carried out with green- and red-tagged allele-specific primers, which were fully compatible with the two-color fluorescence cross-correlation setup at 488 nm and 633 nm excitation wavelengths. RESULTS: The measured data of the amplification mixes (tubes) were normalized as the maximum correlation amplitude of each tube. Correlated and uncorrelated data were optically separated in the amplification mixes by their characteristic correlation times, which significantly differed from each other. The correlated data were generated in the presence of the proper mutated genotype template, whereas uncorrelated data were due to the absence of the proper genotype template. Furthermore, the specific association of the two-color fluorescence correlated signals with the target DNA was experimentally proven. Using this novel two-color cross-correlation approach, the MTHFR genotypes, which were determined in 21 clinical samples, showed concordance with methods involving a PCR-based assay with hexachloro-6-carboxy-fluorescein (HEX)- and 6-carboxy-fluorescein (FAM)-tagged allele-specific primers and a subsequent separation step with capillary electrophoresis, yet are simpler to perform. There was no evidence of a central trend of false-positive or false-negative results. We demonstrated how the novel, ultrasensitive typing system could be applied to studies where researchers are trying to perfect their assays and are often working with the unknown, or application to problematic assays in a clinical environment for those involved in molecular diagnosis. CONCLUSIONS: We present an alternative method to those commonly used in genotyping. Two-color cross-correlation FCS allows the detection of the fluorescence signals specifically associated with the heterozygous mutated, the homozygous mutated, and normal individuals, as exemplified in this study. The presence of nonspecific amplification products, which interfere with subsequent DNA analysis, could therefore highlight the need for two-color cross-correlation FCS as a means of discriminating between specific association of the fluorescence signals with the target DNA and DNA not related to the target.

Base Sequence↗

PubMed2005

Sensitivity to interaural correlation of single neurons in the inferior colliculus of guinea pigs.

Sensitivity to changes in the interaural correlation of 50-ms bursts of narrowband or broadband noise was measured in single neurons in the inferior colliculus of urethane-anaesthetized guinea pigs. Rate vs. interaural correlation functions (rICFs) were measured using two methods. These methods compensated in different ways for the inherent variance in interaural correlation between tokens with the same expected correlation. The shape of all rICFs could be best described by power functions allowing them to be summarized by two parameters. Most rICFs were best fit by a power below 2, indicating that they were only slightly nonlinear. However, there were a few fitted functions that had a power of 3-6, indicating marked curvature. Modeling results indicate that the nonlinearity of the majority of rICFs was explicable in terms of the monaural transduction stages; however, some of the rICFs with power greater than 2 require either multiple inputs to the coincidence detector or additional nonlinearities to be included in the model. Discrimination thresholds were estimated at reference correlations of -1, 0, and +1 using receiver operating characteristic (ROC) analysis of the spike-count distribution at each correlation. Thresholds spanned the full possible range, from a minimum of 0.1 to the maximum possible of 2. Thresholds were generally highest with a reference correlation of -1, intermediate with a reference of 0, and lowest with a reference correlation of +1. Thresholds were lowest for the most steeply sloped rICFs, but thresholds were not strongly correlated to the spike rate variance. The lowest thresholds occurred using narrowband noise that was compensated for internal delays, but they were still about three times larger than human psychophysical thresholds measured using similar stimuli. The data suggest that, unlike pure tone interaural time difference, discrimination of a population measure is required to account for behavioral interaural correlation discrimination performance.

Anesthesia↗

PubMed1990

Within-mouth correlations for indicators of the host response in gingival crevicular fluid.

Gingival crevicular fluid was collected from multiple sites in patients with chronic adult periodontitis, and analysed for the lysosomal enzymes beta-glucuronidase and arylsulphatase, the cytoplasmic enzyme lactate dehydrogenase, total IgA, IgG and IgM and the protease inhibitor alpha 2-macroglobulin. The within-mouth (intraclass) correlation coefficients were calculated to describe the relationship between samples collected from individual patients. Data collected at baseline and 3 months after root planing and scaling were analysed, as was the change between examinations. Volume of crevicular fluid demonstrated the smallest intraclass correlation coefficient (0.16 at baseline, 0.12 at 3 months; 0.11 change), while probing depth and enzyme activity had moderate intraclass correlations (i.e. 0.36, 0.36, 0.26 for beta-glucuronidase). Immunoglobulin and alpha 2-macroglobulin activity in the fluid had the strongest correlations (i.e. 0.64, 0.57, 0.65 for IgG). The correlations for anatomically related teeth within a quadrant (molar, non-molar) were equivalent to or greater than the correlation for all samples within a mouth. Examined by tooth type, the intraclass correlations for volume of crevicular fluid, probing depth, beta-glucuronidase, arylsulphatase and lactate dehydrogenase were higher for non-molar teeth. In contrast, intraclass correlations for IgA, IgG, IgM and alpha 2-macroglobulin in samples from molar teeth were either equivalent to or greater than the correlations for non-molar samples. Calculation of intraclass correlation coefficients for such data can (1) indicate the degree of variability present in multiple samples of crevicular fluid collected from individual patients, (2) provide information about the source of host mediators in the fluid, and (3) help identify appropriate sampling strategies for the fluid.

Adult↗

PubMed1992

The sequential hypothesis of sleep function. IV. A correlative analysis of sleep variables in learning and nonlearning rats.

Female adult rats were trained for a two-way active avoidance task (4 h), and allowed free sleep (3 h). Control rats (C) were left in their home cages during the acquisition period. Dural electrodes and an intraventricular cannula, implanted one week in advance, were used for EEG recording during the period of sleep and for the injection of [3H]thymidine at the beginning of the training session, respectively. Rats were killed at the end of the sleep period, and the DNA-specific activity was determined in the main brain regions and in liver. Correlations among sleep, behavioral and biochemical variables were assessed using Spearman's nonparametric method. In learning rats (L), the number of avoidances was negatively correlated with SS-W variables, and positively correlated with SS-PS variables (episodes of synchronized sleep followed by wakefulness or paradoxical sleep, respectively) and with PS variables. An inverse pattern of correlations was shown by the number of escapes or freezings. No correlations occurred in rats unable to achieve the learning criterion (NL). In L rats, the specific activity of brain DNA was negatively correlated with SS-W variables and positively correlated with SS-PS variables, while essentially no correlation concerned PS variables. On the other hand, in NL rats, comparable correlations were positive with SS-W variables and negative with SS-PS and PS variables. Few and weak correlations occurred in C rats. The data support a role of SS in brain information processing, as postulated by the sequential hypothesis on the function of sleep. In addition, they suggest that the elimination of nonadaptive memory traces may require several SS-W episodes and a terminal SS-PS episode. During PS episodes, adaptive memory traces cleared of nonadaptive components may be copied in more suitable brain sites.

Animals↗

PubMed2005

Correlation between the adiponectin-leptin ratio and parameters of insulin resistance in patients with type 2 diabetes.

We studied the correlation between the adiponectin-leptin (A/L) ratio and parameters of insulin resistance in 220 Japanese patients with type 2 diabetes (138 men and 82 women). Body mass index (BMI), triglycerides (TGs), HDL cholesterol (HDL), and preheparin serum lipoprotein lipase (LPL mass) were examined as laboratory parameters of the insulin resistance. The correlations between these laboratory parameters and adiponectin, leptin, or A/L ratio were studied. Adiponectin levels correlated significantly with BMI (r = -0.298, P = .0003), TGs (r = -0.221, P = .0092), HDL (r = 0.31, P = .0002), and LPL mass (r = 0.26, P = .0021) in men, and with TGs (r = -0.29, P = .0093), HDL (r = 0.239, P = .0338), and LPL mass (r = 0.499, P < .0001) in women. Leptin levels correlated significantly with only BMI (r = 0.31, P = .0002) in men, and with BMI (r = 0.71, P < .0001) and TGs (r = 0.26, P = .0201) in women. Adiponectin and leptin levels tended to correlate with these parameters in an opposite manner. On the other hand, A/L ratio significantly correlated with BMI (r = -0.4, P < .0001), TG (r = -0.199, P = .0192), HDL (r = 0.235, P = .0054), and LPL mass (r = 0.244, P = .0390) in men, and with BMI (r = -0.482, P < .0001), TG (r = -0.402, P = .0002), HDL (r = 0.358, P = .0011), and LPL mass (r = 0.487, P < .0001) in women. Next, the patients were divided into 3 groups classified by their fasting plasma glucose (FPG) level, and the correlations between the parameters and A/L ratio or homeostasis model assessment (HOMA-R), and the correlation between A/L ratio and HOMA-R were investigated in each group. Significant correlations between the parameters and A/L ratio were tended to be observed as the FPG level rose; however, the significant correlations between the parameters and HOMA-R were no longer seen as FPG level elevated. The results suggested that the A/L ratio was effective in relevance as a parameter of insulin resistance to adiponectin or leptin alone, and a more sensitive and reliable marker of insulin resistance than HOMA-R as the FPG level elevated, in patients with type 2 diabetes.

Adiponectin↗

PubMed1999

Normal tissue complication probabilities correlated with late effects in the rectum after prostate conformal radiotherapy.

PURPOSE: Radiation therapy of deep-sited tumours will always result in normal tissue doses to some extent. The aim of this study was to calculate different risk estimates of late effects in the rectum for a group of cancer prostate patients treated with conformal radiation therapy (CRT) and correlate these estimates with the occurrences of late effects. Since the rectum is a hollow organ, several ways of generating dose-volume distributions over the organ are possible, and we wanted to investigate two of them. METHODS AND MATERIALS: A mathematical model, known as the Lyman-Kutcher model, conventionally used to estimate normal tissue complication probabilities (NTCP) associated with radiation therapy, was applied to a material of 52 cancer prostate patients. The patients were treated with a four field box technique, with the rectum as organ at risk. Dose-volume histograms (DVH) were generated for the whole rectum (including the cavity) and of the rectum wall. One to two years after the treatment, the patients completed a questionnaire concerning bowel (rectum) related morbidity quantifying the extent of late effects. RESULTS: A correlation analysis using Spearman's rank correlation coefficient, for NTCP values calculated from the DVHs and the patients' scores, gave correlation coefficients which were not statistically significant at the p<0.01 level. The correlation coefficients based on histograms of the whole rectum were larger than those derived from histograms of the rectum wall. Also, simpler descriptive measures as Dmax, of the whole rectum, correlated better to observed late toxicity than Dmax derived from histograms of the rectum wall. Correlation coefficients from "high-dose" measures were larger than those calculated from the NTCP values. Accordingly, as the volume parameter of the Lyman-Kutcher model was reduced, raising the impact of small high-dose volumes on the NTCP values, the correlation between observed effects and NTCP values became significant at p<0.01 level. CONCLUSIONS: 1) High-dose levels corresponding to small volume fractions of the cumulative dose-volume histograms were best correlated with the occurrences of late effects in the rectum as measured with questionnaires. This is compatible with a more serial organisation of the rectal tissue architecture than previously reported. 2) Reducing the Lyman-Kutcher model's volume parameter, thus allowing small high-dose regions to determine the NTCP, improved the correlation, but not beyond that of high-dose levels corresponding to small volume fractions of the cumulative dose-volume histograms.

Diarrhea↗

PubMed2001

Neuronal integration mechanisms have little effect on spike auto-correlations of cortical neurons.

Cortical neurons of behaving animals generate irregular spike sequences, but the sequences generally differ from an entirely random sequence (Poisson process), and they have temporal correlations (spike auto-correlations). Temporally correlated spike sequences can be brought about because of incoming synaptic inputs to the neuron, or because of the neuronal integration mechanism. In this paper, we attempt to determine which is the origin of spike auto-correlations observed in the spiking data recorded from neurons in the prefrontal cortex of a monkey preserving a cue information in the delay response task experiment. Each incoming input is assumed to be independent from its own spike events, and the temporal integration in the neuron is assumed to be reset by every spike event. So, the process to spike is assumed to be divided into two processes: the process independent from its own spikes, which drives the process reset by its own spikes. Under these assumptions, it is found that the spike-independent process needs to have temporal correlations, through examinations of two kinds of correlation coefficient of consecutive inter-spike intervals. It is also found that the spike-reset process has little effect on the spike auto-correlations and the interval distributions. This suggests that the spike auto-correlation does originate in the temporal correlation of incoming synaptic inputs and the neuronal integration mechanism has little effect on the spike auto-correlation.

Action Potentials↗

PubMed2006

Gender differences in correlations among cardiovascular risk factors.

BACKGROUND: Although the clustering of a few specific cardiovascular risk factors is known as the metabolic syndrome, sex-specific differences in correlations among risk factors have not been thoroughly examined. OBJECTIVE: The analysis was undertaken to detect gender differences in correlations among cardio-vascular risk factors. METHODS: Correlations among age, body mass index, systolic and diastolic blood pressures, and serum levels of fasting blood sugar (FBS), triglycerides (TG), high- and low-density lipoprotein cholesterol, high-sensitivity C-reactive protein (CRP), and uric acid were analyzed in apparently healthy Japanese men and women with TG<400 mg/dL and FBS<126 mg/dL. RESULTS: Among the 136 men and 136 women examined, the frequency of significant correlations was marginally higher in women than in men: 28/45 correlations versus 17/45 correlations, respectively (P=0.017). Of a total of 45 possible correlations, 5 were marginally or significantly stronger in women, whereas no correlations among these risk factors were marginally or significantly stronger in men (P=0.021). These gender differences were considerably attenuated after adjustment for age. However, a significant sex-specific difference was observed in the correlation between TG and rank transformation of CRP, even after adjustment for age (P<0.01). CONCLUSIONS: Correlations among cardiovascular risk factors were marginally stronger in women than in men. These results suggest that the existence of 1 additional risk factor may increase the risk of cardiovascular disease more steeply in women than in men.

Adult↗

PubMedDate not supplied

Monitor-to-monitor temporal correlation of air pollution and weather variables in the North-Central U.S.

Numerous time series studies have reported associations between daily ambient concentrations of air pollution and morbidity or mortality. Recent personal exposure studies have also reported relatively high longitudinal correlation between personal exposures to particulate matter (PM) and home outdoor PM concentrations, lending support to the health effects reported in time series studies. However, the question remains as to how well the temporal fluctuations in the air pollution levels observed at an outdoor monitor represent the temporal fluctuations in the population exposures to pollution of outdoor origins in a city, and how such representativeness affects the size and significance of risk estimates. Also, such spatio-temporal correlations would vary from pollutant to pollutant, likely influencing their relative significance of statistical associations with health outcomes. In this study, we characterized the extent of monitor-to-monitor correlation over time among multiple monitoring sites for PM less than 10 microm (PM10), gaseous criteria pollutants, and several weather variables in seven central and eastern contiguous states (IL, IN, MI, OH, PA, WI, and WV) during the study period of 1988-1990. After removing seasonal trends, the monitor-to-monitor temporal correlation among the air pollution/weather variables within 100-mile separation distance in these areas could be generally ranked into three groups: (1 ) temperature, dew point, relative humidity (r>0.9); (2) O3, PM10, NO2 (r: 0.8-0.6); and (3) CO, SO2 (r<0.5). Using the subsets for separation distance less than 100 miles, regression analyses of these monitor-to-monitor correlation coefficients were also conducted with explanatory variables including separation distance, qualitative (land use, location setting, and monitoring objectives) and quantitative (large and small variance) site characteristics, and region indicators for Air Quality Control Region (AQCR). The separation distance was a significant predictor of monitorto-monitor correlation decline especially for PM10 and NO2 (approximately 0.2 drop over 30 miles). Site characteristic variables were, in some cases, significant predictors of monitor-to-monitor correlation, but the magnitude of their impacts was not substantial. Regional differences, as examined by AQCR, were in some cases (e.g., in Metropolitan Philadelphia) substantial. In these areas, the pollutants that had generally poor monitor-to-monitor correlation in the overall seven states data (i.e., for SO2 and CO) showed higher monitor-to-monitor correlations, comparable with PM10 and O3, within the AQCR. These results are useful in interpreting some of the past time series epidemiological results. The differences in monitor-to-monitor correlations found across pollutants in this work (i.e., r approximately 0.8 vs. r approximately 0.4) are sufficiently large that they could be a factor in the different pollutant significance levels reported in the epidemiologic literature. It is recommended that future epidemiological studies collect and incorporate information on spatial variability among air pollutants in the analysis and interpretation of their results.

Air Pollution↗