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PubMed1988

Effect of maternal and infant covariates on sibship correlation in birth weight.

Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.

Adult↗

PubMed1993

Assessment of adiposity in an Indian population: familial correlations.

Familial correlations for five measures of adiposity were assessed using data from 473 nuclear families residing in the Chittoor district of Andhra Pradesh, India. Fat patterning, measured as the ratio of trunk to extremity subcutaneous fat, and the ratio of the subscapular to the sum of the subscapular and suprailiac skinfolds, and three measures of generalized fatness: body mass index, the sum of six skinfolds and the sum of three trunk skinfolds were analyzed. Maximum likelihood estimates of the familial correlations were obtained for each phenotype, after adjusting for the effects of (1) age within sex, and (2) current levels of energy intake and expenditure, and age within sex. Hypotheses regarding sex-specific, and generational differences in these correlations were assessed for each phenotype, under both adjustment schemes. The strength and pattern of the familial correlations for the three measures of generalized fatness were markedly influenced by the specific adjustments applied to the data. In contrast, the familial correlations for the fat patterning phenotypes were quite similar under the two adjustment schemes. Comparison of our results with previously published data indicates that the familial correlations for a subset of these adiposity measures may be heterogeneous across populations.

Adipose Tissue↗

PubMed2003

Correlation of neuropsychological evaluation and SPECT imaging in patients with Alzheimer's disease.

BACKGROUND: Mini-Mental State Examination (MMSE) is a very useful tool for diagnosing changes in cognitive functions by the general practitioner or other medical staff who is not familiar with neuropsychological tests. On the other hand, HMPAO brain SPECT has been shown to have a high sensitivity to detect neurodegenerative processes, which lead to dementia. The correlation between both methods is unknown. We compared both methods in order to find a rational evaluation tool for the practitioner to obtain a higher efficacy and cost effective way of using both methods. PATIENTS AND METHODS: Fifty-one patients diagnosed as having Alzheimer's disease (AD) were examined. Each patient underwent MMSE analysis, as well as HMPAO brain SPECT. The severity of SPECT abnormalities was categorized into mild, moderate and severe. Statistical analysis was performed in order to evaluate the correlation between imaging findings and neuropsychological testing. RESULTS: Marginal inverse correlation was found between global MMSE SPECT imaging on right and left side (p = 0.05) and the left temporal region (p = 0.05). MMSE subgroup component of orientation was highly significantly inversely associated with SPECT imaging of right and left frontal region (p > 0.0001). The MMSE subgroup of immediate memory was significantly correlated to left and right temporal regions (p = 0.001 and p = 0.002 respectively). Age was not significantly correlated to global MMSE or any of its subtest components. CONCLUSION: MMSE score has no linear correlation to SPECT perfusion findings. In cases of abnormal orientation score subgroup SPECT imaging is not recommended. In most instances, a combination of both methods should be employed by the general practitioner for further evaluation of dementia.

Aged↗

PubMed2003

Regional cerebral blood flow correlations of somatosensory areas 3a, 3b, 1, and 2 in humans during rest: a PET and cytoarchitectural study.

The concept of functional connectivity relies on the assumption that cortical areas that are directly anatomically connected will show correlations in regional blood flow (rCBF) or regional metabolism. We studied correlations of rCBF of cytoarchitectural areas 3a, 3b, 1, and 2 in the brains of 37 subjects scanned with PET during a rest condition. The cytoarchitectural areas, delineated from 10 postmortem brains with statistical methods, were transformed into the same standard anatomical format as the resting PET images. In areas 3a, 3b, and 1, somatotopically corresponding regions were intercorrelated. Area 2 was correlated with the dorsal pre-motor area. These results were in accordance with the somatosensory connectivity in macaque monkeys. In contrast, we also found correlations between areas 3b and 1 with area 4a, and SMA, and among the left and right hand sector of areas 3a, 3b, and 1. Furthermore, there were no correlations between areas 3b, 1, and 2 with SII or other areas in the parietal operculum, nor of other areas known to be directly connected with areas 3a, 3b, 1, and 2 in macaques. This indicates that rCBF correlations between cortical areas during the rest state only partly reflect their connectivity and that this approach lacks sensitivity and is prone to reveal spurious or indirect connectivity.

Adult↗

PubMed2003

Modeling intra-subject correlation among repeated scans in positron emission tomography (PET) neuroimaging data.

Many in vivo positron emission tomography (PET) neuroimaging studies record correlates of regional cerebral blood flow (rCBF) in a series of scans for each individual, usually under different experimental conditions. Typical methods for statistical analysis involve fitting voxel-specific general linear models (GLM) that assume spherical normal errors, implying that all voxel-specific rCBF measurements are independent and arise from identical normal probability distributions. While the spherical GLM provides a unified and computationally efficient approach to estimation, the likely correlations among an individual's repeated scans and heteroscedasticity between conditions prompt the use of extended statistical methodology. We outline a more general method to analyze PET data using random effects and correlated errors to model unequal variances across conditions as well as covariances (correlations) among the repeated scans for each individual. We introduce correlation maps to display intra-subject correlations between an individual's rCBF measurements from different scans. We illustrate the application of our model using data from a study of social anxiety and highlight analytical advantages over the spherical GLM.

Cerebrovascular Circulation↗

PubMed2007

'Prefrontal' cognitive performance of healthy subjects positively correlates with cerebral FDOPA influx: an exploratory [18F]-fluoro-L-DOPA-PET investigation.

Dopamine neurotransmission influences those cognitive processes, which are generally regarded as prefrontal cortical functions. In previous positron-emission-tomography (PET) studies, net blood-brain clearance of [18F]-fluoro-l-DOPA (FDOPA) correlated with impaired cognitive performance in patients with Parkinson's disease or schizophrenia. We hypothesized that FDOPA influx also correlates with performance of cognitive tasks associated with prefrontal functioning in healthy volunteers. The net blood-brain clearance of FDOPA (K(in)(app)) was mapped in a group of 11 healthy volunteers and calculated in striatal volumes-of-interest. The Wisconsin-Card-Sorting-Test (WCST), Stroop-Test, Trail-Making-Test (TMT-A/B), and Continuous-Performance-Test (CPT-M) had been administered previously to the same subjects. No correlation of K(in) (app) with perseverative errors in WCST or age could be found. However, there were significant positive correlations between the magnitude of K(in)(app) in caudate nucleus, putamen, and midbrain with performance of the TMT-B, CPT-M, and the Stroop test. Highest correlations were found between the time needed to perform the Stroop interference task and the K(in)(app) of striatal areas (Caudate nucleus: -0.780, P = 0.005; putamen: -0.870, P < 0. 001). Thus, the present findings reveal a strong correlation between dopamine synthesis capacity in striatum of healthy volunteers and performance of cognitive tasks linked to the prefrontal cortex.

Adult↗

PubMed1988

Correlation patterns of cancer relative frequencies with some socioeconomic and demographic indicators in Brazil: an ecologic study.

Sex-specific relative frequencies (RF) of oral, esophageal, stomach, colon, rectal, laryngeal, lung, female breast, cervical and penile cancers obtained from a government-sponsored, nation-wide data base of histopathological diagnoses were evaluated with respect to all possible inter-site correlations and with 12 socioeconomic and demographic variables for 23 States in Brazil. Use of bivariate and multivariate methods detected a high positive intercorrelation among RFs of lung, laryngeal and colon cancers regardless of sex. RFs for these 3 sites were also positively correlated with many markers of State development and affluence. Cervical and penile cancers emerged as a distinct subset with respect to their correlation patterns. RFs for these neoplasms were highly (positively) correlated (r = 0.8606, p less than 0.001) with each other and exhibited intense negative associations with many of the affluence markers and the former cancer sites. Bivariate correlations generally exhibited a better fit with female-specific RFs than with data from males which was reflected in the number of strong correlations detected by sex.

Brazil↗

PubMed2001

MRI assessment of microvascular characteristics in experimental breast tumors using a new blood pool contrast agent (MS-325) with correlations to histopathology.

A new contrast medium, MS-325, was compared to albumin-(Gd-DTPA)(30) in 18 chemically induced rat breast tumors based on quantitative estimates of microvascular permeability (K(PS)) and fractional plasma volume (fPV) using a two-compartment bidirectional model. No significant correlation was found between MS-325-enhanced microvascular assays with either tumor grade or with microvascular counts (MVCs). In comparison, the correlation coefficient between K(PS) and histologic tumor grade using albumin-(Gd-DTPA)(30) (r =.58) was statistically significant (P <.01). Also, using albumin-(Gd-DTPA)(30), a significant correlation (r =.55, P <.05) was observed between the K(PS) and MVC, a biomarker of angiogenesis. Correlations between fPV and MVC were not statistically significant for either contrast medium. In conclusion, using MS-325, no significant correlations between the MR-estimated permeability values or plasma volumes were observed in experimental breast tumors with either the histologic tumor grade or MVC. This analysis confirms our previous determination that capillary permeability estimates, using a prototype large molecular contrast medium, albumin-(Gd-DTPA)(30), correlate significantly with both histologic tumor grade and MVC.

Animals↗

PubMed2006

Dynamic MR perfusion and proton MR spectroscopic imaging in Sturge-Weber syndrome: correlation with neurological symptoms.

PURPOSE: To investigate physiological alterations in Sturge-Weber syndrome (SWS) using MR perfusion imaging (PWI) and proton spectroscopic imaging (MRSI), and their association with neurological status. MATERIALS AND METHODS: Six consecutive patients with a clinically established diagnosis of SWS underwent MRI using a 1.5 Tesla scanner. The protocol consisted of conventional anatomic scans, dynamic PWI, and multislice MRSI. A pediatric neurologist evaluated the neurological scores, and the imaging results were correlated with neurological scores using nonparametric correlation analysis. RESULTS: Two patients had classic neuroimaging findings of unilateral cerebral atrophy with corresponding leptomeningeal enhancement and hypoperfusion (prolonged mean transit time). Two patients had bilateral disease, and two had normal symmetric perfusion. Among clinical measures, the highest correlation was between hemiparesis index and hypoperfused tissue volume (Spearman's correlation coefficient, rho = 0.943, P < 0.05). There was also a trend of correlation, although not statistically significant (P = 0.06), between the hemiparesis score and the NAA/Cr ratio in the mid to posterior centrum semiovale, lateral gray matter (GM), and splenium. CONCLUSION: In SWS, PWI indicates cerebral hypoperfusion predominantly due to impaired venous drainage, with only the most severely affected regions in some patients also showing arterial perfusion deficiency. The extent and severity of the perfusion abnormality and neuronal loss/dysfunction reflect the severity of neurological symptoms and disability, and the highest correlation is found with the degree of hemiparesis. These parameters may be useful as quantitative measures of disease burden; however, further studies in larger number of patients (and with a more homogeneous age range) are required to confirm the preliminary findings reported here.

Adolescent↗

PubMed1990

Correlations of regional postmortem enzyme activities with premortem local glucose metabolic rates in Alzheimer's disease.

Correlations were sought between local cerebral metabolic rates (LCMRs) for glucose in various regions of the cortex, determined in premortem PET scans, with the regional activities of choline acetyltransferase (ChAT), acetylcholinesterase (AChE), beta-glucuronidase (Gluc, a probable index of reactive gliosis), and phosphate-activated glutaminase (PAG, a possible indice of the large pyramidal neurons) measured on postmortem tissue. Significant negative correlations between LCMRs and Gluc activities were found in 6 PET-scanned cases of Alzheimer disease (AD), and positive correlations of LCMRs with PAG were found in 5. By contrast, a positive correlation with ChAT and AChE was found in only 1. The results are consistent with the metabolic deficits in AD being primarily a reflection of local neuronal loss and gliosis. Similar data on two cases of Huntington's disease showed no significant correlations, while 1 patient with Parkinson dementia showed a significant (negative) correlation only with Gluc.

Aged↗

PubMed1995

Texture correlation: a method for the measurement of detailed strain distributions within trabecular bone.

A new technique, termed texture correlation, is described for the measurement of displacement and strain patterns within samples of trabecular bone. Texture correlation is a modification of digital image correlation, a method for analysis of deformation in objects marked with random surface speckle. Instead of surface speckle, the trabecular pattern itself is used as a basis for correlation. Digitized contact radiographs of samples in unloaded and loaded states are compared by computer to determine displacements of a grid of points. Displacements are filtered with Savitsky-Golay polynomial-convolution filters to reduce noise, and then strain is calculated with finite element techniques. The method is conceptually similar to the manual measurement of surface markers but has numerous advantages: no marking of the sample is required, displacements are measured automatically by computer, measurement of thousands of displacements is practical, and filtering allows calculation of strain over small regions of the sample. The validity of the technique is demonstrated by comparison of strain patterns measured by texture correlation at low resolution with the same patterns measured by a surface marker technique in six samples of trabecular bone from a human femoral head. The results of texture correlation at full resolution then are presented to demonstrate the capabilities of the method.

Femur Head↗

PubMed2005

Improved methods for 1H-3H heteronuclear shift correlation.

A better understanding of the structure of complex 3H-labeled molecules can be obtained by complete assignment of their 1H and 3H solution-state NMR spectra. The assignment process is aided by the detection of heteronuclear chemical shift correlations between 1H and 3H nuclei. Heteronuclear correlation (HETCOR) experiments previously applied to this task exhibit several drawbacks caused by the nature of both the pulse sequences and 1H-3H spin systems. The range of J-couplings involved in 1H-3H coupling networks make it challenging to perform correlation experiments using methods that rely on coherences created during free precession periods and interrupted by transfer pulses. Two alternative HETCOR experiments are demonstrated for 1H-3H systems in the present work and are shown to have advantages over earlier methods. The first experiment is known as hetero-TOCSY and correlates heteronuclear chemical shifts using J-cross polarization. This experiment achieves both homonuclear and heteronuclear mixing and connects the chemical shifts of all 1H and 3H nuclei in a coupling network. A second HETCOR experiment uses the heteronuclear Overhauser effect to obtain through-space correlations between nearby nuclei. The 1H-3H HETCOR experiments are phase sensitive and typically contain more correlations than other methods, which is beneficial for assignment purposes, while being sensitive enough to be applicable to routine analytical samples. The experiments were used to analyze 3H incorporation in sub-milligram quantities of 3H-labeled pharmaceutical derivatives with complex labeling schemes.

Hydrogen↗

PubMed2003

Computing oxygen-enhanced ventilation maps using correlation analysis.

Correlation maps of oxygen-enhanced ventilation were obtained in nine healthy volunteers using complete and selected image series. The complete series included all images acquired with the subjects alternately inhaling room air and 100% oxygen. The selected series were the subsets of the complete series and included only co-registered images that showed matched diaphragmatic position at maximal expiration. Cross-correlation was computed between the time response function of each pixel and the input function representing the alternation between periods of room air and 100% oxygen inhalation. The confidence level for the correlation analysis was set to 0.01. Pulmonary parenchymal anatomy was consistently reproduced throughout the lung, even in anterior slices where published data have reported correlation problems. The overall average correlation coefficient was 0.66 +/- 0.07 for the complete series and 0.75 +/- 0.08 for the selected series. It was concluded that correlation analysis could be used to reconstruct qualitative oxygen-enhanced ventilation maps.

Adult↗

PubMed2005

Tissue segmentation and classification of MRSI data using canonical correlation analysis.

In this article an accurate and efficient technique for tissue typing is presented. The proposed technique is based on Canonical Correlation Analysis, a statistical method able to simultaneously exploit the spectral and spatial information characterizing the Magnetic Resonance Spectroscopic Imaging (MRSI) data. Recently, Canonical Correlation Analysis has been successfully applied to other types of biomedical data, such as functional MRI data. Here, Canonical Correlation Analysis is adapted for MRSI data processing in order to retrieve in an accurate and efficient way the possible tissue types that characterize the organ under investigation. The potential and limitations of the new technique have been investigated by using simulated as well as in vivo prostate MRSI data, and extensive studies demonstrate a high accuracy, robustness, and efficiency. Moreover, the performance of Canonical Correlation Analysis has been compared to that of ordinary correlation analysis. The test results show that Canonical Correlation Analysis performs best in terms of accuracy and robustness.

Algorithms↗

PubMed1991

An empirical test of Rogers' original and revised theory of correlates in adolescents.

The purpose of this study was to examine Rogers' original and revised theory of correlates in adolescents. The correlates were measured by Perceived Field Motion, Human Field Rhythms, Creativity, Sentience, Fast Tempo, and Waking Periods. The original theory was tested with data obtained from samples of early (n = 116), middle (n = 116), and late (n = 116) adolescents. The revised theory was tested in a fourth selectively combined sample of adolescents, aged 12 to 21 (n = 89). Data were collected in classroom settings. Although the findings did not support either theory, they did indicate that: (1) four of the six correlates studied performed as correlates when examined in three discrete phases of adolescence, as determined by chronological age, (2) the means of the individual correlates increased slightly in frequency levels developmentally, and (3) the correlates emerged at different frequency levels when examined in adolescents, aged 12 to 21.

Adolescent↗

PubMed2003

Correlation of six different cystic fibrosis chest radiograph scoring systems with clinical parameters.

In past decades, several chest radiograph scoring systems for cystic fibrosis were developed. This study was performed to compare interobserver variability of six different radiograph scores and to correlate them with clinical parameters. Thirty chest radiographs of 30 patients with cystic fibrosis were scored according to Shwachman-Kulczycki scoring, Chrispin-Norman scoring, adjusted Chrispin-Norman scoring, Brasfield scoring, Wisconsin scoring, and the Northern scoring system by two independent observers. Data on clinical parameters such as lung function, nutritional status, and infectious exacerbation rate, obtained simultaneously with the chest radiograph, were reviewed. Interobserver variability was low (Pearson's correlation coefficients, 0.76-0.84; all P < 0.01), and scores had good limits of agreement (Bland and Altman). Correlation of radiograph score with clinical parameters was good for most pulmonary function test data (correlation coefficients from 0.72-0.78 for percent of forced expired volume in 1 sec (FEV(1)%) predicted and from 0.69-0.74 for FVC% predicted) and for infectious exacerbation rate (correlation coefficients from 0.68-0.73). All six radiograph scoring systems, especially the Chrispin-Norman score, showed a low interobserver variability and correlated well with lung function tests, especially FEV(1)% predicted and infectious exacerbation rate, and moderately with maximum work capacity and thoracic mobility.

Adolescent↗

PubMed1995

Prostate specific antigen in a community-based sample of men without prostate cancer: correlations with prostate volume, age, body mass index, and symptoms of prostatism.

The correlation between both prostate specific antigen levels (PSA) and prostate specific antigen density (PSAD) and age, prostate volume parameters, body mass index, and the International Prostate Symptom Score (IPSS) were studied in a community-based population. A sample of 502 men aged 55 through 74 years was evaluated, excluding those with a serum PSA above 10 ng/ml, those with biopsy proven prostate cancer, and those who had previously undergone a prostate operation. PSA and PSAD did not correlate with the body mass index. Weak correlations were found between PSA and age (r = 0.25; P < 0.001), PSAD and age (r = 0.17; P < 0.001) and between PSA and the total prostate volume (r = 0.58; P < 0.001). PSA did not correlate independently with age after adjustment for volume (P = 0.22). The finding that PSAD correlates with age (r = 0.17; P < 0.001) is partly explained by the incomplete volume adjustment of PSAD which is proved by the positive correlation between PSAD and prostate volume (r = 0.26; P < 0.001). In the main target age-range for prostate cancer screening there is a poor basis for the use of age-specific reference values or volume adjustment for PSA levels in order to increase the clinical usefulness of this serum marker. Comparison of the results of the present study and studies conducted in others regions shows that there may be significant differences in PSA values per age stratum. Further studies are needed to clarify the reasons for these differences.

Aged↗

PubMed1995

An analysis of side chain interactions and pair correlations within antiparallel beta-sheets: the differences between backbone hydrogen-bonded and non-hydrogen-bonded residue pairs.

Cross-strand pair correlations are calculated for residue pairs in anti-parallel beta-sheet for two cases: pairs whose backbone atoms are hydrogen bonded together (H-bonded site) and pairs which are not (non-H-bonded site). The statistics show that this distinction is important. When glycine is located on the edge of a sheet, it shows a 3:1 preference for the H-bonded site. The strongest observed correlations are for pairs of disulfide-bonded cystines, many of which adopt a close-packed conformation with each cystine in a spiral conformation of opposite chirality to its partner. It is likely that these pairs are a signature for the family of small, cystine-rich proteins. Most other strong positive and negative correlations involve charged and polar residues. It appears that electrostatic compatibility is the strongest factor affecting pair correlation. Significant correlations are observed for beta- and gamma-branched residues in the non-H-bonded site. An examination of the structures shows a directionality in side chain packing. There is a correlation between (1) the directionality in the packing interactions of non-H-bonded beta- and gamma-branched residue pairs, (2) the handedness of the observed enantiomers of chiral beta-branched side chains, and (3) the handedness of the twist of beta-sheet. These findings have implications for the formation of beta-sheets during protein folding and the mechanism by which the sheet becomes twisted.

Amino Acids↗