Comparison of a direct enzymatic assay and polyacrylamide tube gel electrophoresis for measurement of small, dense low-density lipoprotein cholesterol.

BACKGROUND: Small, dense low-density lipoprotein cholesterol (sdLDL-C) has been linked to the progression of cardiovascular disease. We compared two methods for determination of sdLDL-C, a direct enzymatic (ENZ) method and a polyacrylamide tube gel electrophoresis (PGE) assay, and investigated the associations of both sdLDL-C measurements with metabolic syndrome. METHODS: We analyzed 242 patient sera for sdLDL and atherosclerosis-related markers. The PGE method separates the intermediate-density lipoprotein particles into three midbands (MID-A to MID-C) and the LDL particles into seven subfractions (LDL1 to LDL7); the sdLDL-PGE result is calculated as the sum of cholesterol concentrations from LDL3 to LDL7. RESULTS: The regression equation for sdLDL-C was [ENZmmol/L]=0.779[PGE]+0.67, r=0.713. ENZ showed higher sdLDL-C concentrations than PGE (0.86±0.33 vs. 0.24±0.32 mmol/L); however, the difference was not associated with sdLDL-C concentration (p=0.290). sdLDL-C, as measured with the enzymatic assay, exhibited significant positive correlations with very-low-density lipoprotein, MID-C, MID-B, and LDL2 (all p<0.001), considered atherogenic lipoproteins, but did not correlate with the less atherogenic lipoproteins MID-A and LDL1 (all p>0.600). The ENZ and PGE methods yielded similar patterns of correlation between sdLDL-C, and atherosclerosis-related markers. Using logistic regression, sdLDL-ENZ and apolipoprotein B were identified as significant predictors of metabolic syndrome (p<0.03). CONCLUSIONS: The ENZ assay for sdLDL-C correlated well with the PGE method. The ENZ method measures a broader range of atherogenic lipoprotein particles than PGE and has the potential to identify subjects with vascular risk, thus contributing in directing specific interventions for cardiovascular prevention.

Burden and frequency of viral testing of kidney and non-kidney transplant recipients.

Transplant patients are at risk of infections due to long-term immunosuppression contributing to morbidity and mortality in this population. Post-transplant testing guidelines were established to monitor and guide therapeutic interventions in transplant recipients. We hypothesize that there are gaps in adherence to the recommended frequency of laboratory testing in post-transplant patients. We analyzed national reference laboratory data to compare viral post-transplant infection (PTI) testing frequency with their respective published guidelines to understand patient uptake and compliance. We evaluated the ordering patterns, positivity rates, and frequency of molecular infectious disease tests (MIDTs). We included 345 patients with International Classification of Diseases (ICD)-10 codes for transplant (Z940-Z942, Z944, Z9481, Z9483, Z9484) with at least two tests (within 7 days) in January 2019 and at least one test in December 2020 to find patients in the post-transplant period. We analyzed two cohorts: kidney transplant recipients (KTRs; 40%) and non-KTR (60%) then followed them longitudinally for the study period. In KTR cohort, high-to-low proportion of ordered MIDT was blood BK virus (bBKV) followed by cytomegalovirus (CMV); in non-KTR cohort, CMV was followed by Epstein-Barr virus (EBV). KTR cohort positivity was highest for urine BK virus (uBKV; 58%) followed by EBV (46%), bBKV (40%), and CMV (31%). Non-KTR cohort positivity was highest for uBKV (64%), EBV (51%), CMV (30%), bBKV (8%), and adenovirus (7%). All patients were tested at progressively longer intervals from the date of the first post-transplant ICD-10-coded test. More than 40% of the KTR cohort were tested less frequently for EBV and bBKV, and more than 20% of the non-KTR cohort were tested for EBV less frequently than published guidelines 4 months after transplant. Despite regular testing, the results of MIDT testing for KTR and non-KTR patients in the post-transplant period are not aligned with published guidelines.IMPORTANCEGuidance for post-transplant infectious disease testing is established, however, for certain infections it allows for clinician discretion. This leads to transplant center policies developing their own testing/surveillance strategies based on their specific transplant patient population (kidney, stem cell, etc.). The Organ Procurement and Transplant Network (OPTN) has developed a strategic plan to improve and standardize the transplant process in the US to improve outcomes of living donors and recipients. Publishing national reference lab data on the testing frequency and its alignment with the recommended guidelines for post-transplant infectious diseases can inform patient uptake and compliance for these strategic OPTN efforts.

Risk Estimation of Severe COVID-19 Based on Initial Biomarker Assessment Across Racial and Ethnic Groups.

CONTEXT.­: Disease courses in COVID-19 patients vary widely. Prediction of disease severity on initial diagnosis would aid appropriate therapy, but few studies include data from initial diagnosis. OBJECTIVE.­: To develop predictive models of COVID-19 severity based on demographic, clinical, and laboratory data collected at initial patient contact after diagnosis of COVID-19. DESIGN.­: We studied demographic data and clinical laboratory biomarkers at time of diagnosis, using backward logistic regression modeling to determine severe and mild outcomes. We used deidentified data from 14 147 patients who were diagnosed with COVID-19 by polymerase chain reaction SARS-CoV-2 testing at Montefiore Health System, from March 2020 to September 2021. We generated models predicting severe disease (death or more than 90 hospital days) versus mild disease (alive and fewer than 2 hospital days), starting with 58 variables, by backward stepwise logistic regression. RESULTS.­: Of the 14 147 patients, including Whites, Blacks, and Hispanics, 2546 (18%) patients had severe outcomes and 3395 (24%) had mild outcomes. The final number of patients per model varied from 445 to 755 because not all patients had all available variables. Four models (inclusive, receiver operating characteristic, specific, and sensitive) were identified as proficient in predicting patient outcomes. The parameters that remained in all models were age, albumin, diastolic blood pressure, ferritin, lactic dehydrogenase, socioeconomic status, procalcitonin, B-type natriuretic peptide, and platelet count. CONCLUSIONS.­: These findings suggest that the biomarkers found within the specific and sensitive models would be most useful to health care providers on their initial severity evaluation of COVID-19.

Porcine pancreas: a superior source of cholesterol esterase for total serum cholesterol assay by the enzymatic kinetic method.

BACKGROUND: Accurate determination of cholesterol requires complete hydrolysis of cholesteryl esters and must be very fast for the kinetic cholesterol assay. We investigated the properties of cholesterol esterase derived from Pseudomonas fluorescens, Candida cylindracea, bovine pancreas, and porcine pancreas for cholesterol determination in human serum. METHODS: Optimization of four enzymes and effect of sodium cholate concentration were performed. We evaluated and compared their performances in enzymatic kinetic cholesterol determination. RESULTS: The optimal sodium cholate concentration was 3, 5, 15, and 12 mmol/l with the enzyme activities at 200, 100, 100, and 100 U/l for P. fluorescens, C. cylindracea, bovine pancreas, and porcine pancreas, respectively. Linearity obtained from all enzymes was up to 16.3 mmol/l. All assays were compared favorably with standardized endpoint method. Only the cholesterol esterase derived from porcine pancreas demonstrated acceptable precision within the acceptable criteria (%CV < 3.0). Also, this esterase was least affected by interfering substances and showed longer stability than that of C. cylindracea and bovine pancreas. CONCLUSION: Porcine pancreas cholesterol esterase is superior to that obtained from P. fluorescens, C. cylindracea, and bovine pancreas for total serum cholesterol determination by the kinetic method because of its lower cost, better accuracy and precision, less interference, and longer stability.

Association between liver and chronic kidney disease on hemoglobin A1c concentrations.

INTRODUCTION: HbA1c is the gold standard for measuring long-range glycemic control in patients with type-2 diabetes mellitus. Conditions such as CKD or LD can lead to spurious HbA1c test results. There is conflicting literature about the relationship between HbA1c, LD, and CKD. METHODS: Results for HbA1c concentrations were retrieved from 2015- to 2019. We evaluated over 2,500 test results with LD and 20,000 results with CKD compared to over 21,000 test results without LD, iron deficiency anemia, or CKD. Patients were classified as having LD if they had high ALT and AST concentrations and classified as CKD, if they have abnormal serum creatinine and BUN or low eGFR based on age-based reference ranges. Kruskal-Wallis statistical analyses method was used to test whether the two populations followed the same distribution and significance. RESULTS: The median HbA1c concentration was 5.8% (40 mmol/l) among LD classified patients in both males and females vs. 5.4% (36 mmol/l) (P < 0.001) for females and 5.6% (38 mmol/l) (P < 0.001) for males without LD. A significant difference in median HbA1c concentrations were also observed between CKD samples (female: 5.7% (39 mmol/l), male: 6.0% (42 mmol/l)) and non-CKD samples (female: 5.4% (36 mmol/l), male: 5.6% (38 mmol/l)) (P < 0.001). Depending on the population's CKD stage, median concentrations of % HbA1c are increased from stage-1 through stage-4 and fell in Stage-5. CONCLUSION: Patients with high AST and ALT concentrations or CKD can have increased HbA1c concentrations compared to normal patients. When using HbA1c concentrations to monitor diabetes, healthcare professionals should consider LD or CKD status before making any therapeutic decisions.

Large-scale retrospective analyses of the effect of iron deficiency anemia on hemoglobin A1c concentrations.

INTRODUCTION: HbA1c is a reliable biomarker for diagnosing and prognosis of diabetes, but many clinical scenarios and interfering factors can affect the test results. Any conditions that affect red cell turnover, such as iron-deficiency anemia (IDA), can lead to spurious HbA1c results. Reports on how IDA affects HbA1c concentrations are contradictory, and to understand better the association between HbA1c concentrations and IDA, we conducted a large-scale retrospective study. METHODS: Test results for HbA1c concentrations were retrieved from the years 2015-2019. We evaluated over 12,000 patients with IDA and 21,000 patients without IDA. Patients were classified as having IDA if samples with below the age-based ranges for serum iron, ferritin, or transferrin iron saturation and above age-based ranges for transferrin iron-binding capacity or transferrin concentrations. Kruskal-Wallis statistical analyses method was used to test whether the two samples follow the same distribution and significance. RESULTS: The median HbA1c concentration was 5.7% among IDA classified patients and 5.4% among normal samples (P < 0.001) for females. For males, the median HbA1c concentration was 6.0% among IDA classified patients and 5.6% among normal samples (P < 0.001). CONCLUSION: Patients classified as IDA can have increased HbA1c concentrations than patients without IDA. Clinicians should consider IDA status before making therapeutic decisions based on HbA1c concentrations.

Contributions of Glucose and Hemoglobin A1c Measurements in Diabetes Screening.

OBJECTIVES: Given the long-term consequences of untreated diabetes, patients benefit from timely diagnoses. Payer policies often recognize glucose but not hemoglobin A1c (HbA1c) for diabetes screening. This study evaluates the different information that glucose and HbA1c provide for diabetes screening. METHODS: We conducted a retrospective review of national clinical laboratory testing during 2020 when glucose and HbA1c were ordered for routine diabetes screening, excluding patients with known diabetes, out-of-range glucose, or metabolic syndrome. RESULTS: Of 15.47 million glucose and HbA1c tests ordered simultaneously, 672,467 (4.35%) met screening inclusion criteria; 116,585 (17.3%) were excluded because of diabetes-related conditions or the specimen was nonfasting, leaving 555,882 result pairs. More than 1 in 4 patients 60 years of age or older with glucose within range had an elevated HbA1c level. HbA1c claims were denied more often for Medicare beneficiaries (38,918/65,273 [59.6%]) than for other health plans combined (23,234/291,764 [8.0%]). CONCLUSIONS: Although many health plans do not cover HbA1c testing for diabetes screening, more than 1 in 4 glucose screening patients 60 years of age or older with an in-range glucose result had a concurrent elevated HbA1c result. Guideline developers and health plans should explicitly recognize that glucose and HbA1c provide complementary information and together offer improved clinical utility for diabetes screening.

Retrospective Performance Analyses of over Two Million U.S. QuantiFERON Blood Sample Results.

Both the QuantiFERON-TB Gold Plus (QFT-Plus) and the QuantiFERON-TB Gold In-Tube (QFT-GIT) tests are interferon gamma (IFN-γ) release assays (IGRAs) intended to detect in vitro cell-mediated immune responses to Mycobacterium tuberculosis antigens. In this study, we retrospectively analyzed performance data for both the QFT-GIT and QFT-Plus test systems from over 2 million samples. QFT-Plus and QFT-GIT testing was performed as specified in the respective package inserts at 23 Quest Diagnostics sites. Blood specimens were collected from individuals in all 50 states from November 2018 through December 2019. Retrospective analyses compared the proportion of positive, indeterminate, and conversion/reversion results. The overall proportion of QFT-positive results was 7% for both the QFT-Plus and QFT-GIT. The proportion of positive results was highest for QFT-GIT (7.5%) followed by the heparin 1-tube QFT-Plus (7.2%); a lower proportion of positives was observed with the 4-tube (all four QFT tubes were used in blood collection) QFT-Plus (6.0%). The proportions of indeterminate results for the 1-tube (heparin-only tube collection) and 4-tube QFT-Plus methods were less than 1% and 4%, respectively. This study indicates a higher proportion of positive results for M. tuberculosis than data from other studies. Additionally, the proportion of indeterminate QFT results were markedly lower when the sample was transported in one lithium-heparin tube instead of direct inoculation into 4 QFT-Plus tubes at the site of blood collection. IMPORTANCE In this study, we retrospectively analyzed results from both the QFT-GIT and QFT-Plus test systems from over 2 million blood specimens. The variables analyzed were (i) QFT positivity rates among various U.S. populations, (ii) indeterminate rates among various types of blood draws and how often an indeterminate result was resolved within 30 days after the initial draw, and (iii) the association of TB1 and TB2 antigen tubes with IGRA reversion and conversion events from serial QFT testing. This is, to our knowledge, the largest QFT study representing patients from an extensive geographic coverage across the United States and U.S. territories.

Association of CETP Gene Variants with Atherogenic Dyslipidemia Among Thai Patients Treated with Statin.

OBJECTIVE: Patients treated with statins for dyslipidemia may still have a residual risk of atherosclerotic cardiovascular disease (ASCVD). To determine whether genetic variants in the cholesteryl ester transport protein (CETP), rs3764261 (C>A), rs708272 (G>A), and rs12149545 (G>A) affect ASCVD risk, we studied the association of these variants with dyslipidemia in statin-treated patients. PATIENTS AND METHODS: We included 299 adult Thai patients treated with a statin (95 men and 204 women). Genotyping was performed by conducting a TaqMan real-time polymerase chain reaction-based analysis. We used logistic regression models adjusted for potential confounders of age, body mass index, blood pressure, insulin resistance, and statin dosage to analyze the association between CETP variants and atherogenic lipoprotein patterns. RESULTS: CETP polymorphisms of rs3764261 and rs708272, but not rs12149545, were significantly associated with high-density lipoprotein cholesterol (HDL-C), apoA-I, triglycerides, very low-density lipoprotein (VLDL)-C, and large LDL (LDL1-C) levels as well as mean LDL particle size (all p < 0.020). However, no significant difference was observed in total cholesterol, LDL-C, or apoB levels by CETP variants. Regardless of sex, the combination of rs3764261 (CC genotype) and rs708272 (GG or GA genotypes) showed a stronger association with atherogenic dyslipidemia, including features of decreased HDL-C, elevated triglycerides, and LDL subclass pattern B (odds ratio [OR] = 2.99, 95% confidence interval [CI]: 1.78-5.02) compared with the single variant rs3764261 (OR = 2.11, 95% CI: 1.27-3.50) or rs708272 (OR = 2.12, 95% CI: 1.29-3.49). CONCLUSION: The polymorphisms of CETP rs3764261 (CC genotype) and rs708272 (GG and GA genotypes) may have a higher susceptibility to atherogenic dyslipidemia. Testing for CETP rs3764261 and rs708272 may serve as a surrogate marker for lipid management in statin-treated patients, which may help individualize treatment for reducing the residual risk of ASCVD.

SARS-CoV-2 positivity rates associated with circulating 25-hydroxyvitamin D levels.

Until treatment and vaccine for coronavirus disease-2019 (COVID-19) becomes widely available, other methods of reducing infection rates should be explored. This study used a retrospective, observational analysis of deidentified tests performed at a national clinical laboratory to determine if circulating 25-hydroxyvitamin D (25(OH)D) levels are associated with severe acute respiratory disease coronavirus 2 (SARS-CoV-2) positivity rates. Over 190,000 patients from all 50 states with SARS-CoV-2 results performed mid-March through mid-June, 2020 and matching 25(OH)D results from the preceding 12 months were included. Residential zip code data was required to match with US Census data and perform analyses of race/ethnicity proportions and latitude. A total of 191,779 patients were included (median age, 54 years [interquartile range 40.4-64.7]; 68% female. The SARS-CoV-2 positivity rate was 9.3% (95% C.I. 9.2-9.5%) and the mean seasonally adjusted 25(OH)D was 31.7 (SD 11.7). The SARS-CoV-2 positivity rate was higher in the 39,190 patients with "deficient" 25(OH)D values (<20 ng/mL) (12.5%, 95% C.I. 12.2-12.8%) than in the 27,870 patients with "adequate" values (30-34 ng/mL) (8.1%, 95% C.I. 7.8-8.4%) and the 12,321 patients with values ≥55 ng/mL (5.9%, 95% C.I. 5.5-6.4%). The association between 25(OH)D levels and SARS-CoV-2 positivity was best fitted by the weighted second-order polynomial regression, which indicated strong correlation in the total population (R2 = 0.96) and in analyses stratified by all studied demographic factors. The association between lower SARS-CoV-2 positivity rates and higher circulating 25(OH)D levels remained significant in a multivariable logistic model adjusting for all included demographic factors (adjusted odds ratio 0.984 per ng/mL increment, 95% C.I. 0.983-0.986; p<0.001). SARS-CoV-2 positivity is strongly and inversely associated with circulating 25(OH)D levels, a relationship that persists across latitudes, races/ethnicities, both sexes, and age ranges. Our findings provide impetus to explore the role of vitamin D supplementation in reducing the risk for SARS-CoV-2 infection and COVID-19 disease.

Association between polymorphisms of LEP, LEPR, DRD2, HTR2A and HTR2C genes and risperidone- or clozapine-induced hyperglycemia.

OBJECTIVE: To determine whether genetic polymorphisms related to pharmacodynamics with metabolic adverse effects, namely leptin promoter (LEP) rs7799039, leptin receptor rs1137101, dopamine D2 rs4436578, serotonin 5-HT2A rs6313, and serotonin 5-HT2C rs518147 and rs12836771, are associated with hyperglycemia induced by risperidone or clozapine in adult Thai patients with psychosis. METHODS: A total of 180 patients treated with risperidone-based (n=130) or clozapine-based (n=50) regimens were included in this study. Blood samples were analyzed for genotyping of the candidate genes and biochemical testing. Genotyping was performed by conducting a TaqMan real-time polymerase chain reaction-based analysis. RESULTS: The prevalence of hyperglycemia was higher in patients receiving clozapine (64.0%) than in those receiving risperidone (30.8%). Among the candidate genes, only the LEP rs7799039 polymorphism demonstrated a significant association with hyperglycemia (χ2=9.879, P=0.008) in patients treated with risperidone; patients with the AA genotype had the highest risk (41.1%), followed by those with AG (20.8%) and GG (0%) genotypes. Using the recessive genetic model (AA vs AG + GG), the odds ratio and 95% CI were 3.28 and 1.44 -7.50, respectively. None of the genes were associated with hyperglycemia in patients treated with clozapine. A binary logistic regression revealed that the LEP rs7799039 polymorphism demonstrated a significant association with hyperglycemia, independent of body-mass index (BMI) in patients receiving risperidone; the odds ratio (95% CI) was 3.188 (1.399-7.262), P=0.006. By contrast, none of the pharmacodynamic genetic factors, except for BMI, were significantly associated with hyperglycemia in patients receiving clozapine. CONCLUSION: The risk of type 2 diabetes mellitus is associated with the LEP rs7799039 polymorphism in Thai adults receiving risperidone but not in those receiving clozapine. Clarifying underlying mechanisms and risk of hyperglycemia provides an opportunity to prevent impaired glucose metabolism in patients receiving risperidone or clozapine.

Performance of body mass index and percentage of body fat in predicting cardiometabolic risk factors in Thai adults.

BACKGROUND: Body mass index (BMI) and percentage of body fat (PBF) are used to measure obesity; however, their performance in identifying cardiometabolic risk in Southeast Asians is unclear. Generally, Asian women have higher PBF and lower BMI than do men and other ethnic populations. This study was conducted to address whether a discord exists between these measures in predicting obesity-related cardiometabolic risk in a Thai population and to test whether associations between the measures and risk factors for cardiovascular disease have a sex-specific inclination. METHODS: A total of 234 (76 men and 158 women) outpatients were recruited. BMI obesity cutoff points were ≥25.0 and ≥27.0 kg/m2 and PBF cutoff points were ≥35.0% and ≥25.0% for women and men, respectively. Blood samples were analyzed for total cholesterol, triglycerides, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, lipoprotein subclasses, apolipoprotein A-I, apolipoprotein B, glucose, hemoglobin A1c, insulin, high-sensitive C-reactive protein (hsCRP), adiponectin, leptin, and 25-hydroxyvitamin D. RESULTS: Twenty-five percent of participants classified as normal-BMI had excessive fat, whereas 9% classified as normal-PBF had excessive BMI. Good relationships were found between BMI and PBF using sex stratification (R2 >0.5). The prevalence of metabolic syndrome was markedly increased in overweight and/or excess body fat groups compared with lean group. Logistic regression analyses showed that BMI was the best predictor of hypertension. BMI was an independent predictor of insulin resistance, hyperglycemia, hypertriglyceridemia, and hyperleptinemia in women, whereas PBF was for men. However, PBF proved to be a good indicator for atherogenic lipoprotein particles in both sexes. Notably, neither index predicted increased hsCRP or 25-hydroxyvitamin D insufficiency. CONCLUSION: Considerable sex-specific variations were observed between BMI and PBF in their associations with and predictability of numerous cardiometabolic biomarkers. No single measure provides a comprehensive risk predication as shown herein with the Thai population, and therefore both should be applied in screening activities.

Advantages and disadvantages of serum cholesterol determination by the kinetic vs the end point method.

Enzymatic assays for cholesterol determination can use an end point or a kinetic method. We evaluated and compared the performance of these methods. We constructed user-defined methods on 3 automated analyzers using Streptomyces cholesterol reagents to evaluate the analytic performance of both methods. Linearity (700-900 mg/dL) and stability of reagents (5-11 weeks) depended on the analyzers. The coefficients of variation for imprecision were 2.41% to 2.99% and 3.78% to 5.52% for the end point and kinetic methods, respectively. The end point method showed less bias at decision cut points (-0.8% to 1.3%) than did the kinetic method (-1.1% to 3.6%) but was more affected by interfering substances.The advantages of the end point over the kinetic method are better precision and lower reagent cost. The end point imprecision fell within National Cholesterol Education Program guidelines (

Using the single-compartment ratio model to calculate half-life, NT-proBNP as an example.

BACKGROUND: The single-compartment model offers a simple way to calculate the half-life of a compound if it is secreted or injected at the known rate compared with another compound whose half-life is known. This model may be easier to use than the exponential decay model. Investigators disagree on the value of the half-life of NT-proBNP, with published values ranging from 70 to 120 min. Prior studies used values from sheep, which may not be appropriate in humans. Therefore, we have re-evaluated the half-life of NT-proBNP using a single-compartment model. METHODS: The single-compartment model allows one to evaluate the half-life of NT-proBNP using the NT-proBNP:BNP ratio and the BNP half-life. We calculated the NT-proBNP:BNP ratio from 26 subjects without cardiac abnormalities. RESULTS: The mean ratio of the NT-proBNP to BNP was 1.24 with an SEM of 0.1. Using a half-life of 20 min for BNP, the calculated half-life for NT-proBNP would be 24.8 min. CONCLUSIONS: The single-compartment ratio model requires neither strictly first-order decay after stimulation, nor the collection of times samples. The re-calculated half-life for NT-proBNP is 25 min for humans, which differs greatly from the current literature value of 90 min and thus its half-life is closer to that of BNP in normal subjects. Accordingly its estimated time to return to a steady-state after a disturbance is 100 min, and therefore it could be useful in the monitoring of patients over short time periods. The single-compartment ratio model is fairly robust in the presence of cross-reactivity.

The clearance of BNP modeled using the NT-proBNP-BNP relationship.

BACKGROUND: The ventricular myocardium simultaneously secretes two natriuretic peptides useful in the evaluation of heart failure: BNP, hormonally active, and NT-proBNP, the N-terminal end, non-hormonally active, but ultimately their concentrations differ and their clearance patterns are poorly defined. METHODS: We measured NT-proBNP and BNP in patients with and without heart failure and compared their concentrations using regression analysis. RESULTS: The relationship between NT-proBNP with BNP is nonlinear. Between 45 and 70 pmol of BNP/L (class II heart failure) the slope is much higher than in other ranges and the NT-proBNP/BNP ratio reaches its maximum in patients with class II NYHA heart failure. CONCLUSIONS: The difference in concentration for NT-proBNP and BNP can be related to the diffusion across the renal basement membrane. Their ratio is nonlinear because BNP is cleared faster than in patients with class II heart failure than other classes or normal, suggesting a change in a non-renal mode of clearance.

Associations of aerobic and strength exercise with clinical laboratory test values.

OBJECTIVES: Physical exercise may affect levels of blood-based biomarkers. However, exercise status is seldom considered in the interpretation of laboratory results. This study reports the associations between habitual exercise participation and clinical laboratory test results. METHODS: The effects of days per week of aerobic and strength exercise participation on laboratory test results for 26 biomarkers in young adults aged 18 to 34 years (n = 80,111) were evaluated using percentile distribution analyses and multivariate regression. RESULTS: In both men and women, more days per week of either aerobic or strength exercise were significantly associated with lower levels of glucose, hemoglobin A1c, LDL cholesterol, total cholesterol, triglycerides, estimated glomerular filtration rate, globulin, and C-reactive protein, and significantly higher levels of HDL cholesterol, creatinine, iron, and percent saturation (all p < .05). Type of exercise or gender influenced the observed relationships with exercise frequency for total cholesterol, aspartate aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, uric acid, bilirubin, and iron binding capacity. CONCLUSIONS: Physical exercise shifted the distribution of results into the direction suggestive of better health. Reported relationships may help clinicians and patients to better understand and interpret laboratory results in athletic populations and possibly re-evaluate interpretation of reference intervals for physically active populations.

Impact of risperidone on leptin and insulin in children and adolescents with autistic spectrum disorders.

OBJECTIVE: To evaluate the influence of dose and duration of risperidone treatment on cardiovascular and diabetes risk biomarkers in children and adolescents with autistic spectrum disorders (ASDs). DESIGN AND METHODS: In this cross-sectional analysis, a total of 168 ASDs patients (89% male) treated with a risperidone-based regimen for ≥12months were included. Blood samples were analyzed for glucose and lipid metabolic markers, adiponectin, leptin, prolactin, cortisol and high sensitive C-reactive protein. RESULTS: The mean concentrations of glucose, insulin, prolactin and leptin and HOMA-IR significantly rose with risperidone dosage (all P<0.025), but those of adiponectin and cortisol did not. Using regression analysis, insulin, leptin, prolactin and glucose concentrations and HOMA-IR show significant association with dosage. None of the markers except adiponectin showed dependence on duration of treatment. However, insulin and leptin concentrations and HOMA-IR clearly increased with increasing both dosage and duration. Dosage and duration of treatment had minimal effect on standard lipid profile and lipoprotein subclasses. CONCLUSIONS: Risperidone treatment disturbed glucose homeostasis and endocrine regulation (particularly leptin) in children and adolescents with ASDs, in a dose- and duration-dependent manner, being suggestive of leptin and insulin resistance mechanisms. Metabolic adverse effects, especially development of type 2 diabetes mellitus should be closely monitored, particularly in individuals receiving high doses and/or long-term risperidone treatment.

Modified plasma-based ecarin clotting time assay for monitoring of recombinant hirudin during cardiac surgery.

Recombinant hirudin (r-hirudin) is being used increasingly for therapeutic anticoagulation in patients with heparin-induced thrombocytopenia undergoing cardiovascular surgery. Although multiple laboratory methods are available for measuring r-hirudin, the ecarin clotting time (ECT) is the most commonly used for this purpose. Ecarin (extracted from snake venom) converts prothrombin to meizothrombin, which promotes clot formation. Direct thrombin inhibitors, like r-hirudin, bind meizothrombin and yield a linear, dose-dependent prolongation of ECT. Low levels of prothrombin and fibrinogen in plasma samples can lead to higher ECT; suggesting falsely elevated r-hirudin levels. A modified ECT assay with prothrombin and fibrinogen in excess was optimized using an orthogonal array method to eliminate the variations in patients' plasma prothrombin and/or fibrinogen levels for accurate determinations of plasma r-hirudin levels. By using the modified ECT assay, falsely elevated r-hirudin levels can be avoided in patients undergoing cardiopulmonary bypass, thus providing reliable and accurate r-hirudin monitoring in this clinical setting.

Application of Streptomyces and Brevibacterium cholesterol oxidase for total serum cholesterol assay by the enzymatic kinetic method.

BACKGROUND: Using non-esterified cholesterol standard, Brevibacterium and Streptomyces are found as suitable sources of cholesterol oxidase for kinetic cholesterol assay. For clinical use, we investigated the suitability of these enzymes for cholesterol determination in human serum. METHODS: We compared the performance of reagents containing 2 enzymes for the kinetic determination of total serum cholesterol with the standardized endpoint method. RESULTS: Reagent containing Streptomyces enzyme was more sensitive than that of Brevibacterium, with linearity up to 20.7 and 2.6 mmol/l, respectively. The analytical reaction for Streptomyces showed a shorter lag phase (148 s) and a steeper slope (absorbance vs. time) than that of Brevibacterium (246 s). The assay using Streptomyces reagent was precise and accurate and compared favorably with the endpoint method (y=1.06x-0.15, r=0.996, bias=0.21 mmol/l). Hemoglobin as high as 7.5 g/l did not interfere while turbidity greater than 2+ (absorbance >0.778 at 670 nm) and bilirubin concentrations >171.0 micromol/l did interfere (in a negative interference). Reagent was stable up to at least 8 weeks. CONCLUSIONS: The Streptomyces cholesterol oxidase, with 3,4-dichlorophenol, proved a suitable source for serum total cholesterol determination by the kinetic method.

Assessing the Impact of Analytical Error on Perceived Disease Severity.

CONTEXT: The perception of the severity of disease from laboratory results assumes that the results are free of analytical error; however, analytical error creates a spread of results into a band and thus a range of perceived disease severity. OBJECTIVE: To assess the impact of analytical errors by calculating the change in perceived disease severity, represented by the hazard ratio, using non-high-density lipoprotein (nonHDL) cholesterol as an example. DESIGN: We transformed nonHDL values into ranges using the assumed total allowable errors for total cholesterol (9%) and high-density lipoprotein cholesterol (13%). Using a previously determined relationship between the hazard ratio and nonHDL, we calculated a range of hazard ratios for specified nonHDL concentrations affected by analytical error. RESULTS: Analytical error, within allowable limits, created a band of values of nonHDL, with a width spanning 30 to 70 mg/dL (0.78-1.81 mmol/L), depending on the cholesterol and high-density lipoprotein cholesterol concentrations. Hazard ratios ranged from 1.0 to 2.9, a 16% to 50% error. Increased bias widens this range and decreased bias narrows it. CONCLUSIONS: Error-transformed results produce a spread of values that straddle the various cutoffs for nonHDL. The range of the hazard ratio obscures the meaning of results, because the spread of ratios at different cutoffs overlap. The magnitude of the perceived hazard ratio error exceeds that for the allowable analytical error, and significantly impacts the perceived cardiovascular disease risk. Evaluating the error in the perceived severity (eg, hazard ratio) provides a new way to assess the impact of analytical error.