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Biomedical subjects

Christopher P Price

Publications and source records attributed to Christopher P Price.

At least 19 recordsLinked to original sources
PubMed2006

Improving the quality of self-monitoring blood glucose measurement: a study in reducing calibration errors.

BACKGROUND: Two independent studies reported that 16% of people who self-monitor blood glucose used incorrectly coded meters. The degree of analytical error, however, was not characterized. Our study objectives were to demonstrate that miscoding can cause analytical errors and to characterize the potential amount of bias that can occur. The impact of calibration error with three selfblood glucose monitoring systems (BGMSs), one of which has an autocoding feature, is reported. METHODS: Fresh capillary fingerstick blood from 50 subjects, 18 men and 32 women ranging in age from 23 to 82 years, was used to measure glucose with three BGMSs. Two BGMSs required manual coding and were purposely miscoded using numbers different from the one recommended for the reagent lot used. Two properly coded meters of each BGMS were included to assess within-system variability. Different reagent lots were used to challenge a third system that had autocoding capability and could not be miscoded. RESULTS: Some within-system comparisons showed deviations of greater than +/-30% when results obtained with miscoded meters were compared with data obtained with ones programmed using the correct code number. Similar erroneous results were found when the miscoded meter results were compared with those obtained with a glucose analyzer. For some miscoded meter and test strip combinations, error grid analysis showed that 90% of results fell into zones indicating altered clinical action. Such inaccuracies were not found with the BGMS having the autocoding feature. CONCLUSIONS: When certain meter code number settings of two BGMSs were used in conjunction with test strips having code numbers that did not match, statistically and clinically inaccurate results were obtained. Coding errors resulted in analytical errors of greater than +/-30% (-31.6 to +60.9%). These results confirm the value of a BGMS with an automatic coding feature.

Adult↗
PubMed2006

The use of urinary dipstick tests to exclude urinary tract infection: a systematic review of the literature.

Several systematic reviews have examined the use of dipstick tests to diagnose or rule in urinary tract infection (UTI). We examined the evidence relating to the use of urine leukocyte esterase and nitrite tests in adults to exclude or rule out UTI. A search of the literature from 1966 to 2003 revealed 30 studies as containing relevant and suitable information and 23 of these, which used a cut-off of 108 colony-forming units per liter, were combined in a meta-analysis. The leukocyte esterase or nitrite test combination, with one or the other test positive, was used in 14 studies, showed the highest sensitivity and the lowest negative likelihood ratio. While there was significant heterogeneity between the studies, 7 of 14 demonstrated significant decreases in pretest to posttest probability with a pooled posttest probability of 5% for the negative result. In certain circumstances, there is evidence for the use of urinalysis as a rule-out test for UTI.

Carboxylic Ester Hydrolases↗
PubMed2005

Nurse-based evaluation of point-of-care assays for glycated haemoglobin.

BACKGROUND: Various devices are now available to measure glycated haemoglobin (HbA1c) outside of the laboratory. The aim of this study was to assess the performance of these point-of-care instruments in the hands of non-laboratory trained personnel. METHODS: Two nursing staff tested samples from patients attending a diabetes research clinic using the following point-of-care devices for HbA1c-Metrica A1C Now, Bayer DCA 2000, Cholestech GDX and Axis-Shield Nycocard HbA1c. In addition they performed regular analysis of quality control samples. The effects on analytical performance of multiple operators as well as laboratory-trained staff, were also assessed. All measurements were compared to a boronate-affinity HPLC method in the central laboratory. RESULTS: The mean HbA1c difference of the point-of-care devices compared to the laboratory reference method ranged from -0.31% to +0.39%. Only the DCA device had a between batch imprecision of less than 5%. The analytical performance obtained by laboratory staff was similar to nursing staff for 3 devices and better for the Nycocard device. CONCLUSIONS: On the basis of the results obtained by nursing staff, only the DCA of the devices tested, can be recommended for measurement of HbA1c outside of the laboratory.

Chromatography, High Pressure Liquid↗
PubMed2005

Cardiac troponins and renal function in nondialysis patients with chronic kidney disease.

BACKGROUND: Serum cardiac troponin concentrations are commonly increased in end-stage renal disease (ESRD) in the absence of an acute coronary syndrome (ACS). The data on cardiac troponin I (cTnI) are more variable than those for cardiac troponin T (cTnT). There is little information on cardiac troponin concentrations in patients with chronic kidney disease (CKD) who have not commenced dialysis. METHODS: We studied 222 patients: 56 had stage 3 (moderate CKD); 70 stage 4 (severe CKD); and 96 stage 5 (kidney failure). Patients underwent echocardiography and were followed prospectively for a median of 19 months; all-cause mortality was recorded. RESULTS: Overall, serum cTnT was increased above the 99th percentile reference limit in 43% of all CKD patients studied, compared with 18% for cTnI. Serum cTnT and cTnI concentrations were more commonly increased in the presence of more severe CKD (11 and 6 patients in stage 3, 27 and 8 in stage 4, and 57 and 24 in stage 5 (P < 0.0001 and <0.02, respectively). Among 38 patients with detectable cTnI, 32 had detectable cTnT (r(s) = 0.67; P < 0.0001). There was evidence that decreasing estimated glomerular filtration rate increased the odds of having detectable cTnT (P < 0.001) but not cTnI (P = 0.128). There was no evidence to support an adjusted association of detectable cardiac troponins with increasing left ventricular mass index. Increased cTnT (P = 0.0097), but not cTnI, was associated with decreased survival. CONCLUSIONS: Increased cTnT and cTnI concentrations are relatively common in predialysis CKD patients, in the absence of an ACS, including among those with stage 3 disease. The presence of left ventricular hypertrophy alone does not explain these data. Detectable cTnT was a marker of decreased survival.

Aged↗
PubMed2005

Use of protein:creatinine ratio measurements on random urine samples for prediction of significant proteinuria: a systematic review.

BACKGROUND: Proteinuria is recognized as an independent risk factor for cardiovascular and renal disease and as a predictor of end organ damage. The reference test, a 24-h urine protein estimation, is known to be unreliable. A random urine protein:creatinine ratio has been shown to correlate with a 24-h estimation, but it is not clear whether it can be used to reliably predict the presence of significant proteinuria. METHODS: We performed a systematic review of the literature on measurement of the protein:creatinine ratio on a random urine compared with the respective 24-h protein excretion. Likelihood ratios were used to determine the ability of a random urine protein:creatinine ratio to predict the presence or absence of proteinuria. RESULTS: Data were extracted from 16 studies investigating proteinuria in several settings; patient groups studied were primarily those with preeclampsia or renal disease. Sensitivities and specificities for the tests ranged between 69% and 96% and 41% and 97%, respectively, whereas the positive and negative predictive values ranged between 46% and 95% and 45% and 98%, respectively. The positive likelihood ratios ranged between 1.8 and 16.5, and the negative likelihood ratios between 0.06 and 0.35. The cumulative negative likelihood ratio for 10 studies on proteinuria in preeclampsia was 0.14 (95% confidence interval, 0.09-0.24). CONCLUSION: The protein:creatinine ratio on a random urine specimen provides evidence to "rule out" the presence of significant proteinuria as defined by a 24-h urine excretion measurement.

Creatinine↗
PubMed2005

Crystalline polymorph selection and discovery with polymer heteronuclei.

The discovery and selective production of crystalline polymorphs, an outstanding problem in solid-state chemistry, is of great importance industrially in, for example, the manufacture of pharmaceuticals and pigments. Despite considerable efforts, no reliable method exists to produce all of the stable polymorphs of a given compound. Herein, we report methodology to control the phenomenon of crystal polymorphism through the use of diverse libraries of polymer heteronuclei including both commercially available polymers and combinatorially synthesized cross-linked polymers. This new approach for exploring polymorph space offers the advantage of high throughput crystallization to discover multiple polymorphs combined with the ability to selectively produce a given form from a single solvent and temperature condition by simply varying the nature of the polymer substrate. This technique is successfully demonstrated on the pharmaceuticals acetaminophen, sulfamethoxazole, and carbamazepine and on the pharmaceutical intermediate 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY). High throughput screening, accomplished by optical microscopy and Raman spectroscopy, identified the selective production of the two stable polymorphs of acetaminophen and all six stable forms of ROY. Furthermore, one new form of carbamazepine and two new forms of sulfamethoxazole were discovered; in these cases, single crystals were obtained enabling the structural characterization of two new tetramorphic systems.

Acetaminophen↗
PubMed2005

Crystal chemistry of VAPOL.

Ligands employed in enantioselective catalysis are capable of displaying rich phase behavior that can significantly impact their properties, both structural and physical. To illuminate these issues in a model system, the solid-state structure and properties of the vaulted biaryl ligand VAPOL were investigated. Racemic VAPOL and solvates with toluene and ethyl acetate were structurally characterized. In addition, two polymorphs of (S)-VAPOL were found, and the crystal packing in these and a very stable CH(2)Cl(2) solvate was elucidated. In contrast to BINOL, the unsolvated forms of the ligand lack classical hydrogen-bonding motifs. Remarkably, the melting point of racemic VAPOL is 86 degrees C higher than that of (S)-VAPOL form I, and there is a 2.0 kcal/mol difference in stability at room temperature, favoring the racemate. These values are at the upper end of those observed in the literature for differences between a racemic/chiral pair.

Journal Article↗
PubMed2005

Use of prostate-specific antigen (PSA) isoforms for the detection of prostate cancer in men with a PSA level of 2-10 ng/ml: systematic review and meta-analysis.

OBJECTIVE: Measurement of serum prostate-specific antigen (PSA) for the detection of prostate cancer has poor specificity in men with PSA levels between 2 and 10 ng/ml. It has been suggested that measurement of the ratio of free to total PSA (f/tPSA) or complexed PSA (cPSA) might offer an improvement. We performed a systematic review and meta-analysis to evaluate the diagnostic performance of these tests among men with PSA levels between 2 and 10 ng/ml. METHODS: Data on sensitivity and specificity were extracted from 66 eligible studies. Likelihood ratios and summary receiver operating characteristic curves were estimated and possible sources of heterogeneity between studies examined. RESULTS: Use of the f/tPSA or the cPSA test improved diagnostic performance among men with a total PSA (tPSA) of 2-4 or 4-10 ng/ml compared to tPSA alone. The diagnostic performance of the f/tPSA test was significantly higher in the tPSA range of 4-10 ng/ml compared to a tPSA range of 2-4 ng/ml (p < 0.01); at a sensitivity of 95%, the specificity was 18% in the 4-10 ng/ml tPSA range and 6% in the 2-4 ng/ml tPSA range. Among studies that measured both isoforms, the diagnostic performance of the f/tPSA test and the cPSA was equivalent in both PSA ranges. CONCLUSIONS: The use of the f/tPSA or cPSA test among men with PSA levels between 2 and 10 ng/ml can reduce the number of unnecessary biopsies whilst maintaining a high cancer detection rate.

Humans↗
PubMed2005

B-type natriuretic peptide (BNP) and amino-terminal proBNP in patients with CKD: relationship to renal function and left ventricular hypertrophy.

BACKGROUND: Most patients with chronic kidney disease (CKD) develop cardiovascular complications. Natriuretic peptides are novel markers that can be used to identify and monitor heart failure, but the effect of renal disease on these markers is not fully understood. The aim of the present study is to explore the relationship among circulating B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) concentrations and clinical variables in a cohort of patients with CKD. METHODS: Plasma BNP and NT-proBNP concentrations and left ventricular (LV) mass index were measured in 213 predialysis patients with CKD. RESULTS: Plasma BNP and NT-proBNP concentrations increased with declining estimated glomerular filtration rate (GFR; P < 0.0001). Estimated GFR had an independent effect on plasma BNP (P = 0.0028) and, to a greater extent, plasma NT-proBNP (P < 0.0001) concentrations: mean BNP concentration increased by 20.6% per 10-mL/min/1.73 m2 (0.17-mL/s) reduction in estimated GFR compared with 37.7% for NT-proBNP. NT-proBNP/BNP ratio increased with CKD stage (P < 0.0001). Median plasma BNP and NT-proBNP concentrations were greater in patients with LV hypertrophy (P < 0.0001), and LV mass index had an independent effect on both BNP (P = 0.0223) and NT-proBNP (P < 0.0017). CONCLUSION: Estimated GFR and LV mass index have independent effects on both plasma BNP and NT-proBNP concentrations in patients with CKD. NT-proBNP appears to be affected more by declining kidney function, in keeping with the hypothesis that its clearance is predominantly renal. Our data have significant implications for application of these peptides as cardiac biomarkers in patients with CKD.

Aged↗
PubMed2004

Assessing the clinical impact of prostate-specific antigen assay variability and nonequimolarity: a simulation study based on the population of the United Kingdom.

BACKGROUND: Prostate-specific antigen (PSA) is the most widely used serum biomarker to differentiate between malignant and benign prostate disease. Assays that measure PSA can be biased and/or nonequimolar and hence report significantly different PSA values for samples with the same nominal amount. This report investigates the effects of biased and nonequimolar assays on the decision to recommend a patient for a prostate biopsy based on age-specific PSA values. METHODS: A simulation model, calibrated to the distribution of PSA values in the United Kingdom, was developed to estimate the effects of bias, nonequimolarity, and analytical imprecision in terms of the rates of men who are recommended to have a biopsy on the basis of their assay-reported PSA values when their true PSA values are below the threshold (false positives) or vice versa (false negatives). RESULTS: False recommendation rates for a calibrated equimolar assay are 0.5-0.9% for analytical imprecision between 5% and 10%. Positive bias leads to significant increases in false positives and significant decreases in false negatives, whereas negative bias has the opposite effect. False-positive rates for nonequimolar assays increase from 0.5% to 13% in the worst-case scenario, whereas false-negative rates are almost always 0%. CONCLUSIONS: Biased and nonequimolar assays can have major detrimental effects on both false-negative and false-positive rates for recommending biopsy. PSA assays should therefore be calibrated to the International Standards and be unbiased and equimolar in response to minimize the likelihood of incorrect clinical decisions, which are potentially detrimental for both patient and healthcare provider.

Aged↗
PubMed2004

General principles of pharmaceutical solid polymorphism: a supramolecular perspective.

The diversity of solid-state forms that an active pharmaceutical ingredient (API) may attain relies on the repertoire of non-covalent interactions and molecular assemblies, the range of order, and the balance between entropy and enthalpy that defines the free energy landscape. It is recognized that crystallization is associated with molecular recognition events that lead to self-assembly, and that pharmaceutical function and thermodynamic stability can be altered with a slight change in the interacting molecules or their molecular network motifs. Our current understanding of pharmaceutical solids in terms of molecular recognition and complementarity provides new insights into the design and function of single and fully miscible, multiple-component solids with varying degrees of order, from amorphous to crystalline states, and in this way is leading the path to supramolecular pharmaceutics. This review describes pharmaceutical solids in terms of supramolecular chemistry and crystal engineering concepts, and discusses the events that control crystallization and solid phase transformations.

Butanones↗
PubMed2004

Monitoring the circulating levels of the HER2/neu oncoprotein in breast cancer.

The HER2/neu oncoprotein is a major target for the development of new cancer therapies and is similar to the estrogen receptor, which guides hormone therapy. The HER2/neu status is used to guide therapy decisions in patients with HER2/neu-overexpressing breast cancer tumors. The HER2/neu oncogene, or c-erbB-2, encodes a transmembrane receptor protein that is expressed on normal epithelial cells and can be overexpressed in breast cancer cells. Studies have shown that the extracellular domain (ECD) of the HER2/neu oncoprotein is released from the cell and can be measured in the circulation of women with breast cancer. Enzyme-linked immunosorbent assay methods used to measure the circulating HER2/neu ECD have shown that the prevalence of elevated ECD levels is approximately 18.1% in women with primary breast cancer and approximately 45.6% in women with metastatic breast cancer (MBC). Many studies have monitored the circulating ECD levels after surgery and indicate that increasing ECD levels can indicate recurrence of breast cancer earlier than clinical diagnosis. Studies in women with MBC showed that serial changes in circulating HER2/neu ECD levels paralleled the clinical course of disease, regardless of the treatment regimen. Several studies identified a subgroup of patients with MBC who had HER2/neu-negative disease by tissue testing but developed elevated ECD levels with MBC. In contrast to tissue testing, which is a one-time event, monitoring the circulating levels of the HER2/neu ECD in patients with breast cancer provides a real-time assessment of the HER2/neu status and provides important information for managing the therapy of patients with MBC.

Adult↗
PubMed2003

Application of the principles of evidence-based medicine to laboratory medicine.

The principles of evidence-based medicine and the consequent search for robust evidence on outcomes plays a central role in the practice of laboratory medicine. The core of the evidence lies in an explicit recognition of the clinical question(s) that the test result can address. Studies that focus on the relevant patient cohort and clinical setting for the test, and identify the appropriate outcome measure will generate information that can be used to guide use of the test, identify the benefits, and thereby support the case for investment of resources to deliver the service.

Clinical Laboratory Techniques↗
PubMed2003

The prevalence of myocarditis and skeletal muscle injury during acute viral infection in adults: measurement of cardiac troponins I and T in 152 patients with acute influenza infection.

BACKGROUND: Current literature suggests that myocarditis is a common event during influenza infection, occurring with a prevalence rate of up to 10%, but these studies have relied on relatively nonspecific techniques of varying sensitivities for the detection of myocyte injury. Using measurement of cardiac troponins I and T, this study sought to determine the prevalence of myocarditis in a large unselected cohort of patients with serologically confirmed acute influenza infection. METHODS: A total of 152 subjects were recruited from 60 primary care and university health centers. Serial creatine kinase (CK), CK-MB, and cardiac troponin I and T measurements were taken on days 1, 6, and 21 following presentation. RESULTS: Creatine kinase levels were elevated (mean +/- SD levels, 830 +/- 1531 U/L; range, 181-7280 U/L) during the collection period in 18 patients (12%). Twelve (67%) of these had elevated CK levels on day 1 of presentation. Overall CK-MB levels were higher than 25 U/L in 3 patients with elevated CK readings but in no patient was the CK-MB fraction greater than 6%. Cardiac troponin I and T levels were not raised in any of the patients. CONCLUSIONS: Using more sensitive and specific markers of myocardial injury, we demonstrate that the prevalence of myocarditis during acute influenza infection is substantially lower than previously thought, whereas skeletal muscle injury is relatively common. Although we were unable to conclude that no myocardial inflammation was present, it seems likely that this complication is rare.

Adult↗