Effects of blood collection tubes, including pediatric devices, on 16 common immunoassays.
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Blood Specimen Collection↗
Biomedical subjects
Sihe Wang
Publications and source records attributed to Sihe Wang.
Measurement of serum testosterone using high-performance liquid chromatography/tandem mass spectrometry.
Low levels of serum testosterone typically found in women and children cannot be reliably measured by immunoassay. We developed a simple and sensitive method using high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). Sample preparation involved protein precipitation of serum (1.0 mL) with acetonitrile containing the internal standard (testosterone-d3) followed by liquid extraction with methylene chloride. The chromatographic cycle per specimen was 10 min. The performance was evaluated according to the CLSI EP10-A2 protocol. Within- and between-run imprecision was 20.9%, 2.29% and 1.80%, and 1.81%, 3.58% and 2.97% at mean concentrations of 0.17, 14.1 and 28.8 nM, respectively, with no apparent carryover. The method was linear from 0.21 to 53.1 nM and the analytical recovery was 100.5-106.2% across the concentrations tested. There was no interference observed from other steroids that were tested. Correlation using de-identified patient specimens with a commercial HPLC-MS/MS method showed a slope of 0.991, an intercept of -0.017 and a correlation coefficient (R(2)) of 0.998 by linear regression over concentrations ranging from 0.21 to 16.7 nM. In conclusion, we report here an HPLC-MS/MS method suitable for clinical measurement of serum testosterone.
Chromatography, High Pressure Liquid↗
Evaluation of an immunoassay of whole blood sirolimus in pediatric transplant patients in comparison with high-performance liquid chromatography/tandem mass spectrometry.
BACKGROUND: Sirolimus is widely used as an immunosuppressant, along with calcineurin inhibitors. Because of its variable pharmacokinetics and narrow therapeutic range, therapeutic drug monitoring of sirolimus is critical to optimize its therapeutic effect and to minimize toxicity. Although liquid chromatography/tandem mass spectrometry is considered the method of choice, the technical and financial challenges of this method are obstacles to its use. A microparticle enzyme immunoassay on the Abbott IMx has recently been reintroduced to the clinical diagnostic market. METHODS: We evaluated this immunoassay using high-performance liquid chromatography/tandem mass spectrometry as the reference method. Precision and carryover were evaluated using an expanded CLSI EP10-A2 protocol. Linearity was studied by serial dilution of high-level whole blood samples, and clinical utility was demonstrated by correlation with the reference method using 56 de-identified pediatric patient samples. RESULTS: The total imprecision was less than 12% across the concentrations tested. The method was linear from 2.6 to 31 nM. The immunoassay showed a mean positive bias of 11.5% in patient specimens relative to high-performance liquid chromatography/mass spectrometry (p<0.001), with a correlation coefficient (R) of 0.953. CONCLUSION: We conclude that the reintroduced immunoassay is useful for therapeutic drug monitoring of sirolimus.
Child↗
A fast and simple high-performance liquid chromatography/mass spectrometry method for simultaneous measurement of whole blood tacrolimus and sirolimus.
CONTEXT: Combined immunosuppressant therapy using tacrolimus and sirolimus has demonstrable benefits. Simultaneous chromatographic monitoring of whole blood tacrolimus and sirolimus is useful for reducing reagent consumption and turnaround time. We report here a simple and rapid method using high-performance liquid chromatography/mass spectrometry for simultaneous measurement of whole blood tacrolimus and sirolimus. OBJECTIVE: To develop and validate a high-performance liquid chromatography/mass spectrometry method that is suitable for clinical laboratories and that is simple, rapid, and cost-effective. DESIGN: Whole blood (80 microL) was mixed with zinc sulfate solution, followed by protein precipitation with acetonitrile containing the internal standards. After brief centrifugation, the supernatant (20 microL) was injected onto a C18 guard column. The drug and the internal standard ammonium adducts were monitored by multiple reaction monitoring. One-point calibration at levels of 200 ng/mL (249 nM) tacrolimus and 100 ng/mL (109 nM) sirolimus was prepared by adding tacrolimus and sirolimus to immunosuppressant-free whole blood. RESULTS: The assay took 2.5 minutes per sample injection. The total imprecision was between 2.46% and 7.04% for tacrolimus and between 5.22% and 8.30% for sirolimus across the concentrations tested. No carryover was observed, and recoveries were 92% to 98% for tacrolimus and 100% for sirolimus at all levels tested. The tacrolimus was linear from 0.52 to 155.5 ng/mL (0.65-193.4 nM), and sirolimus was linear from 0.47 to 94.8 ng/mL (0.51-103.7 nM). Biases of correlations with commercial methods were within 7%. CONCLUSIONS: This improved method is simple, fast, cost-effective, and suitable for clinical laboratories. It has been implemented for routine clinical monitoring of posttransplantation immunosuppressant therapy.
Chromatography, High Pressure Liquid↗
Corrections of clinical chemistry test results in a laboratory information system.
CONTEXT: The recently released reports by the Institute of Medicine, To Err Is Human and Patient Safety, have received national attention because of their focus on the problem of medical errors. Although a small number of studies have reported on errors in general clinical laboratories, there are, to our knowledge, no reported studies that focus on errors in pediatric clinical laboratory testing. OBJECTIVE: To characterize the errors that have caused corrections to have to be made in pediatric clinical chemistry results in the laboratory information system, Misys. To provide initial data on the errors detected in pediatric clinical chemistry laboratories in order to improve patient safety in pediatric health care. DESIGN: All clinical chemistry staff members were informed of the study and were requested to report in writing when a correction was made in the laboratory information system, Misys. Errors were detected either by the clinicians (the results did not fit the patients' clinical conditions) or by the laboratory technologists (the results were double-checked, and the worksheets were carefully examined twice a day). No incident that was discovered before or during the final validation was included. On each Monday of the study, we generated a report from Misys that listed all of the corrections made during the previous week. We then categorized the corrections according to the types and stages of the incidents that led to the corrections. RESULTS: A total of 187 incidents were detected during the 10-month study, representing a 0.26% error detection rate per requisition. The distribution of the detected incidents included 31 (17%) preanalytic incidents, 46 (25%) analytic incidents, and 110 (59%) postanalytic incidents. The errors related to noninterfaced tests accounted for 50% of the total incidents and for 37% of the affected tests and orderable panels, while the noninterfaced tests and panels accounted for 17% of the total test volume in our laboratory. CONCLUSION: This pilot study provided the rate and categories of errors detected in a pediatric clinical chemistry laboratory based on the corrections of results in the laboratory information system. A direct interface of the instruments to the laboratory information system showed that it had favorable effects on reducing laboratory errors.
Child↗
Interindividual variability of whole blood viscosity improved with standardized hydration.
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Adolescent↗
Variations of whole blood viscosity using Rheolog-a new scanning capillary viscometer.
BACKGROUND: Whole blood viscosity (WBV) values identify subjects at high risk for initial or recurrent cardiovascular events. However, these measurements have been limited to specialized centers. A new type of viscometer, Rheolog, was designed to overcome the difficulties encountered in WBV measurements using the standard rotational viscometer in a clinical environment. METHODS: We evaluated the 14-day variability of WBV measured by Rheolog in a single-center study of 24 healthy male subjects aged 18-75 years. WBV was measured through an 11-h period on study days 1, 8, and 14. An additional fasting WBV test was performed on study days 3, 5, and 11. RESULTS: Average morning measurements were higher than afternoon measurements at all shear rates. Both inter- and intraindividual variations were higher in the morning than later in the day, but the differences between pooled mean values were not significant. Interindividual variations at fasting were higher than the pre-meal or overall variations. There was a small nonsignificant increase in mean viscosity following each meal. CONCLUSION: WBV measurements using Rheolog have potential for clinical application because of the convenience and low variability of measurements over time.
Adolescent↗
pH effects on measurements of ionized calcium and ionized magnesium in blood.
CONTEXT: It is well known that the concentration of ionized calcium in blood is affected by the pH of the specimen, since hydrogen ions compete with calcium for binding sites on albumin and other proteins. However, the relationship between pH and ionized magnesium concentration is not as well characterized. OBJECTIVE: To determine the effects of pH on ionized magnesium concentration over a wide range of pH values in serum or plasma. DESIGN: Both ionized calcium and ionized magnesium concentrations were measured in 3 sets of samples. (1) Pools of serum or whole blood at different pH values (7.20-7.60) achieved by adding a constant volume of acid or base (diluted solutions of either hydrochloric acid or sodium hydroxide) plus saline. These pools consisted of 2 serum and 3 heparinized whole blood pools collected from leftover blood remaining in clinical specimens in the Clinical Chemistry and Blood Gas Laboratories, respectively, at Duke University Medical Center. (2) Five whole blood specimens obtained from apparently healthy individual donors. (3) Twenty-six whole blood specimens obtained from individual patients (leftover blood from the Blood Gas Laboratory) in which pH was varied by in vitro loss or gain of carbon dioxide. RESULTS: Both ionized calcium and ionized magnesium concentrations decreased as the pH in the specimen increased, indicating the stronger binding of these ions with proteins in the more alkaline environment. CONCLUSION: We conclude that the rate of change of ionized magnesium concentration with pH change (0.12 mmol/L per pH unit) is significantly less than that of ionized calcium (0.36 mmol/L per pH unit). Furthermore, our findings indicate that if adjustment to pH 7.40 is necessary, the ionized magnesium test results need to be adjusted when pH is markedly abnormal, as is sometimes done for ionized calcium.
Calcium↗