Levels Of Quality Control Material Research Articles

Implementation of point-of-care HbA1C instruments into community pharmacies: Initial development of a pathway for robust community testing.

Point-of-care (POC) analysers in community settings can provide opportunistic and regular HbA1c monitoring. Community pharmacies in NHS Scotland are utilised by populations at greatest risk of type two diabetes (T2D). This study describes initial development of an HbA1c pathway using a POC analyser in community pharmacies. The Abbott Afinion analyser was compared in (i) NHS Tayside's Blood Sciences Service and (ii) community pharmacies from four Scottish Health Boards. A side by side comparison with standard operating procedures for HbA1c quantification using 80 T2D patient venous samples. The machine was implemented into 11 community pharmacies and 144 samples obtained from patients for comparison to their recent laboratory HbA1c. Four focus groups examined themes around the intervention and an exit questionnaire was administered. Laboratory assessment verified the efficacy of the POC test machine. The value for level 1 quality control was 44mmol/mol and the mean during testing 42.7mmol/mol. The greatest percent coefficient of variation (cv) was within-run for both levels of quality control material, at a value of 1.63% and 1.62%, respectively. The analyser performed robustly within the pharmacy assessment, with a mean difference of 1.68 and a standard deviation of 0.71 (CV 0.423). Patients with T2D reported positive experiences of using a pharmacy. The focus groups identified an appreciation of the convenience of pharmacies and of the longitudinal relationships with pharmacy staff. POC HbA1c analysers can be successfully established in community pharmacies. The target patient group responded positively to the opportunity to use a pharmacy service.

B-098 Analytical Performance Evaluation of Sigma Strong Clinical Chemistry Assays on the Alinity c System

Abstract Background The aim of this study was to evaluate the analytical performance of 5 Abbott next generation (Sigma Strong) clinical chemistry assays on the Abbott Alinity c system. Method comparison, precision, linearity, accuracy, and sigma metrics were assessed for Albumin BCG2 (Bromocresol green), Albumin BCP2 (Bromocresol purple), Cholesterol2, Total Protein2 and Amylase2. Methods Method comparison between new (second generation) and current on market Alinity assays was performed by measuring 126–138 serum/plasma samples in duplicate. Assessment of imprecision was performed by running 2 levels of quality control material (BioRad; Chemistry UA) and 3 pooled patient samples 5x twice per day for 5 days. 10 replicates of ERM-DA470 k IFCC material for albumin, ERM-AD456 k IFCC material for amylase, NIST SRM 927 material for total protein, and NIST 1951cL1 for cholesterol were run to determine the accuracy and calculated sigma value for each analyte. Linearity testing was performed by running 5–6 levels of commercially available linearity materials in replicates of 3. Bias, acceptable imprecision, and total allowable error were based on Clinical Laboratory Improvement Amendments and Accreditation Canada Diagnostics guidelines. Statistical analysis was performed using EP evaluator. Results Data for method comparison (Passing Bablok), precision (Range of total %CV across 5 concentrations), accuracy (% Bias from target value), and linearity (Range of % recovery) for 5 Abbott second generation clinical chemistry assays are shown in Table 1. All assays demonstrated ≥6 Sigma performance. Conclusion The Abbott second generation (Sigma Strong) clinical chemistry assays on the Alinity c system showed acceptable performance for precision, accuracy, linearity, and agreement with the on-market Alinity c clinical chemistry assays.

B-021 Analytical Performance of Thyroid Function Test on DxI800 System

Abstract Background Thyroid function tests (TFT) which usually include thyroid stimulating hormone (TSH), total triiodothyronine (TT3), and free thyroxine (FT4) are widely applied in clinical practice for screening, diagnosis and monitoring of thyroid disease. We evaluated analytical performance of TSH, TT3, and FT4 using DxI800 (Beckman Coulter, USA) including comparison to Alinity I (Abbott, USA). Methods Precision was determined by percent coefficient of variation (%CV) measuring low, medium, and high levels of quality control material for 5 days with one run per day, 5 replicates per run. Linearity was evaluated using 5 levels of patient serum samples and concentrations were determined by the mean value of two replicates of each level. Method comparison was performed by Passing-Bablok regression using 40 patient serum samples. Results The within-run imprecision at low, medium and high level were 1.50%, 1.77%, and 2.59% for TSH; 4.10%, 2.45%, and 2.84% for TT3; and 3.23%, 2.76%, and 2.19% for FT4. The within-laboratory imprecision at low, medium, and high level were 1.61%, 1.91%, and 2.87% for TSH; 4.33%, 3.73%, and 3.70% for TT3; and 3.36%, 2.76%, and 2.20% for FT4. Linearity of TFT on DxI800 was demonstrated in the range of 0.01–44.68 µIU/mL, 0.09–7.40 ng/mL, and 0.18–5.52 ng/dL for TSH, TT3, and FT4, respectively. Method comparison between DxI800 and Alinity I showed a slope of 1.21 and intercept of 0.05 (correlation coefficient R = 0.994); a slope of 0.95 and intercept of 0.13 (correlation coefficient R = 0.971); and a slope of 1.81 and intercept of −0.88 (correlation coefficient R = 0.969) for TSH, TT3, and FT4, respectively. Conclusion DxI800 showed acceptable performance in terms of precision and linearity for TFT assay including TSH, TT3, and FT4. This study demonstrated that TFT on DxI800 are suitable in clinical laboratory.

ASSESSMENT OF ACCURACY AND PRECISION STATISTICS IN ROUTINE BIOCHEMISTRY AUTOANALYZER USING INTERNAL QUALITY CONTROL SPECIMENS IN A TERTIARY CARE HOSPITAL LABORATORY

Background: Accuracy and precision are two important yardsticks of a reliable analytical system in the clinical laboratory. The study was designed to determine the accuracy and precision statistics of a routine biochemistry auto-analyzer using two levels of quality control materials and to compare these statistics with the company provided values. The study also aimed to compare the month-wise variations in these statistics. Methods: It was a cross-sectional study conducted in the Department of Biochemistry at Birat Medical College Teaching Hospital, Nepal. Laboratory data for the months of May–July, 2021 were retrieved from the laboratory information system (LIS). The retrieved data comprised of the results of two levels of quality control specimens run routinely on Beckman Coulter AU480 biochemistry autoanalyzer for most of the biochemical parameters. Accuracy and precision statistics were calculated as mean and coefficient of variation, respectively. Results: In both levels of control samples, the laboratory determined accuracy statistics were greater in magnitude than the company provided ones for albumin, alkaline phosphatase, aspartate transaminase, creatinine, unsaturated iron binding capacity, urea, direct bilirubin, and amylase; the precision statistics were similarly greater in magnitude for total protein and magnesium. In month-wise comparison of laboratory determined accuracy statistics, the overall mean differences were statistically significant (p<0.05) for all parameters except lactate dehydrogenase and magnesium (both levels of control). Conclusions: The laboratory determined accuracy and precision statistics showed variations from the company provided ones apart from the month-wise variation. Therefore, continuous monitoring of these values is mandatory for ensuring reliable test reports.

Investigation of the Status Quo of Veterinary Point-of-Care Laboratories in Switzerland: Availability, Application, and Quality Management.

The extent to which Swiss veterinary practitioners follow the guidelines for quality assurance of the American Society for Veterinary Clinical Pathology (ASVCP) for point-of-care (POC) testing is unknown. Thus, the aim of this study was to assess the availability, application, and quality management of POC analyzers in Swiss veterinary practices/clinics. For this purpose, we created an online questionnaire on laboratory equipment, quality management, and biosafety, which all members of the Society of Swiss Veterinarians (GST) were invited to complete. In total, 192 clinics/practices participated, of which 69% had automated POC analyzers, mainly for clinical chemistry (99%) and/or hematology (86%). Sample analyses and equipment maintenance were mostly performed by veterinary technicians (81% and 68%, respectively). Reference intervals were adopted from manufacturers (80%) or literature (17%). The results showed that most participants perform basic internal quality control (chemistry: 75%; hematology: 86%), and many use at least two levels of quality control material (47%-48%). Controls are mostly run once a month (chemistry: 36%; hematology: 35%) or ≤4 times/year (36% and 25%). Only three clinics/practices reported participation in an external quality assessment program; comparative testing was more common (chemistry: 42%; hematology: 52%). Only one-quarter of the participants stated that they make use of the data generated through internal and external quality control measures. In conclusion, POC analyzers are widely available in Swiss veterinary clinics/practices, and internal quality control is performed to some extent. However, quality assessment and management and biosafety awareness and measures need to be improved, ideally with the support of clinical pathologists.

Evaluation of the Analytical Performance of Lifotronic H9 Glycated Hemoglobin Analyzer and its Effect on Clinical Decision Making

We aimed to analyze the analytical performance of Lifotronic H9 glycated hemoglobin analyzer (Lifotronic H9) with Arkray Adams HA-8160 glycated hemoglobin analyzer (Arkray HA8160), which is currently used for measurement of HbA1c test in our laboratory. The verification studies of the Lifotronic H9 were performed by comparison with the Arkray HA8160, which has been verified and is already used in our laboratory, and in accordance with the CLSI EP5-A3 and CLSI 15-A3 guidelines. The method comparison study was performed with 316 subjects. Both instruments demonstrated perfect repeatability (within-run) CVs (0.8% - 1.6%), between-run CVs (0.2% - 1.0%), within-day CVs (0.8% - 1.7%), between-day CVs (0.3% - 0.6%), and within laboratory (total im-precision) CVs (0.8% - 1.8%) with two levels of quality control materials. Very good linearity was observed in the method-comparison studies based on Passing-Bablok regression analysis (y = -0.03 + 1.02 x, CUSUM test p = 0.07). Intraclass correlation coefficient (ICC = 0.995) for results and Kappa value (κ = 0.86) for classification of results according to the American Diabetes Association recommendations showed almost perfect agreement. The Lifotronic H9 analyzer shows good precision with lower than recommended total CV 2% and linearity with Arkray HA8160. The Lifotronic H9 is a suitable analyzer for the diagnosis of diabetes and monitoring diabetic control.

Assessment of haematopoietic progenitor cell counting with the Sysmex® XN-1000 to guide timing of apheresis of peripheral blood stem cells.

Successful peripheral blood stem cell (PBSC) collection depends on optimal timing of apheresis, as usually determined by flow cytometry CD34-positive (+) cell count in peripheral blood (PB). Since this method is costly and labour-intensive, we evaluated the use of the Hematopoietic Progenitor Cell count programme on a Sysmex® XN haematologic analyser (XN-HPC) as a rapid and inexpensive alternative for predicting CD34+ cell count in PB samples. Haematopoietic progenitor cell and CD34+ cell counts were compared using 273 PB samples collected from 78 healthy donors and 72 patients who underwent PBSC transplantation. We assessed the effectiveness of the XN-HPC in safely predicting pre-harvest CD34+ counts. The most efficient cut-off values of XNHPC were identified. We also evaluated the imprecision (coefficient of variation, CV) and functional sensitivity. Imprecision of the XN-HPC count was <6.3% on daily measurement of three levels of quality control material. Functional sensitivity was 8.9×106/L. A cut-off value of ≥62×106/L XN-HPC for multiple myeloma (MM) patients and ≥30×106/L for all other subjects had both 100% specificity and 100% positive predictive value for identifying samples with CD34+ cells ≥20×106/L. An XN-HPC threshold of <13×106/L identified preharvest CD34+ cell count <10×106/L with 100% sensitivity and 100% negative predictive value. The XN-HPC is a fast, easy and inexpensive test that can safely improve apheresis workflow thus possibly replacing other more expensive CD34 counts currently performed and promoting optimal timing of PBSC collection.

Analysis of internal quality control data of complete blood count from laboratories participating in national external quality assessment

Objective: To investigate current status and problems of internal quality control (IQC) of complete blood count in China so as to perform IQC normally. Methods: The IQC data of complete blood count for five parameters were collected from laboratories participating in national external quality assessment during 2012-2017 (totally 12 times), including WBC, RBC, Hb, Hct and PLT. After confirmation of all data, data for the 12 times were analyzed as follows.The proportions of using different levels of quality control materials were calculated.The 25th, 50th, 75th, 90th percentiles CV of data collected for the 12 times were calculated respectively and the trends of CV were observed over time.The difference of CV among laboratories running three control levels was compared.The CV of each parameter in 2017 was compared with precision requirements based on biological variation, health standards and German Medical Association Directive; The proportions of laboratories using different control rules were calculated. Results: After invalid data was excluded from those IQC data of laboratories for the 12 times external quality assessment (up to 2 402, as low as 1 449) from 2012 to 2017, the residual data (up to 2 332, as low as 1 431, accounting for 96.0%-99.2%) was used for analysis. 61.9%-66.1%, 18.2%-23.6% and 14.3%-17.3% of laboratories ran one, two and three control levels respectively, and the proportions of laboratories running more than two control levels increased from 33.9% to 38.1%. The decrease trend of the 75th, 90th percentiles CV of WBC, RBC, Hb, Hct for three levels, PLT for normal level and the 90th percentiles CV of PLT low level had statistically significance over time (P<0.05); the decrease trend of the 75th percentiles CV of PLT low level and 75th, 90th percentiles CV of PLT high level had no statistically significance over time. The CV had significant difference between low and normal, low and high control level for WBC and PLT, while there were no difference between normal and high control levels. There were no significant difference of CV among three control levels for RBC, Hb, and Hct. Except for the CV of Hct low, normal level and PLT low level, 85% of laboratories for the other parameters could meet the minimum precision requirements based on biological variation; more than 85% laboratories met the requirements of health standards; except for the CV of PLT low level, more than 80% laboratories met the requirements of German Medical Association Directive. The proportion of laboratories using 1(3s)/2(2s) quality control rules increased from 59.2% to 76.0%. Conclusions: During the past 6 years, the CV for IQC has shown a decrease trend over time. However, the control level and quality control rules used by some laboratories do not meet management requirements. The CV of Hct and PLT in a few laboratories do not meet the minimum requirements of the health standards, and need to implement quality improvements fatherly.

Analytical evaluation of the epoc® point-of-care blood analysis system in cardiopulmonary bypass patients

ObjectivesThe aim of this study was to evaluate the analytical performance of the new epoc® point-of-care blood analysis system in cardiopulmonary bypass patients. Design and methodsThe precision study was conducted on 3 epoc® blood analysis systems using 5 levels of quality control materials twice per day for 5days. The blood specimen was collected in blood gas syringes from 40 cardiac perfusion patients for the comparison study on epoc® (all 3meters), Instrumentation Laboratory GEM4000, Abbott iSTAT, Nova CCX, and Roche Accu-Chek Inform II and Performa glucose meters. ResultsThe epoc® blood analysis systems demonstrated clinically acceptable precision for all analytes (from 0.07%, 0.07%, and 0.13% for pH7.6, 7.4, and 7.0 levels; to 3.87%, 3.74%, and 7.56% for pO2 197, 103, and 56mmHg levels). Comparison studies yielded a correlation coefficient R from 0.9201 (sodium) to 0.9969 (pO2) with the GEM4000; from 0.9071 (sodium) to 0.9965 (potassium) with the iSTAT; from 0.8793 (sodium) to 0.9957 (pO2) with the CCX, and 0.9850 and 0.9904 with Roche Inform II and Performa meters respectively. Average biases for all analytes were within the total allowable error limits. ConclusionThe epoc® blood analysis system is acceptable for point-of-care testing in the cardiovascular surgery setting.

Verification of an immunoturbidimetric assay for heart-type fatty acid-binding protein (H-FABP) on a clinical chemistry platform and establishment of the upper reference limit

BackgroundHeart-type fatty acid-binding protein (H-FABP) is an early biomarker of cardiac injury. Randox Laboratories developed an immunoturbidimetric H-FABP assay for non-proprietary automated clinical chemistry analysers that could be useful in the emergency department. We verified the analytical performances claimed by Randox Laboratories on Roche Cobas 6000 clinical chemistry platform in use in our laboratory, and we defined our own 99th percentile upper reference limit for H-FABP. MethodsFor the verification of method performances, we used pools of spared patient samples from routine and two levels of quality control material, while samples for the reference value study were collected from 545 blood donors. Following CLSI guidelines we verified limit of blank (LOB), limit of detection (LOD), limit of quantitation (LOQ), repeatability and within-laboratory precision, trueness, linearity, and the stability of H-FABP in EDTA over 24h. Results and discussionThe LOQ (3.19μg/L) was verified with a CV% of 10.4. The precision was verified for the low (mean 5.88μg/L, CV=6.7%), the medium (mean 45.28μg/L, CV=3.0%), and the high concentration (mean 88.81μg/L, CV=4.0%). The trueness was verified as well as the linearity over the indicated measurement interval of 0.747–120μg/L. The H-FABP in EDTA samples is stable throughout 24h both at room temperature and at 4°C. The H-FABP 99th percentile upper reference limit for all subjects (3.60μg/L, 95% CI 3.51–3.77) is more appropriate than gender-specific ones that are not statistically different.

Measurement of Serum Total Vitamin D (25‐OH) Using Automated Immunoassay in Comparision With Liquid Chromatography Tandem‐Mass Spectrometry

The associations of vitamin D deficiency with many nonskeletal diseases are still being discovered. We evaluated the use of an automated immunoassay to measure serum total vitamin D (25-OH) and assessed vitamin D status in a Korean adult population. We compared the Elecsys Vitamin D (25-OH) Total Assay (Roche Diagnostics) with liquid chromatography-tandem mass spectrometry (LC-MS/MS) using 300 serum samples. Total imprecision was calculated using three levels of quality control materials and serum samples. We also investigated the vitamin D status using data for 70,762 cases who had a routine health check-up in our hospitals. The regression equation: Elecsys = 0.882 × LC-MS/MS + 6.814 (r = 0.926). Total imprecision was within 10% for all quality control materials and serum samples. The prevalence of vitamin D deficiency using cut-off values of <50 nmol/l (<20 ng/ml) were 70.3% in males and 86.4% in females, respectively. The prevalence of vitamin D deficiency was higher in younger subjects than in older subjects (P for linear-by-linear association was <0.001). Serum vitamin D levels were highest in September and lowest in February. The Elecsys Vitamin D (25-OH) Total Assay was comparable to LC-MS/MS and appropriate for routine clinical use. Vitamin D deficiency is common in Korean adults.

Evaluation of the Performance of ARKRAY ADAMS HA-8180 HbA1cAnalyzer

This article is available from http://www.labmedonline.org 2012, Laboratory Medicine Online This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Hemoglobin (Hb)-A1c is routinely used for the management of diabetes. In 2010, HbA1c was included into the diagnostic criteria for diabetes by the American Diabetes Association. A newly developed HbA1c analyzer, ARKRAY ADAMS HA-8180 (ARKRAY KDK, Japan) was introduced. In this study, we evaluated the analytical performance of ARKRAY ADAMS HA-8180 HbA1c analyzer and compared it with the previously used Variant II Turbo (Bio-Rad Laboratories, USA), which is a National Glycohemoglobin Standardization Program (NGSP) certified analyzer. Methods: According to Clinical Laboratory and Standards Institute (CLSI) evaluation protocol (EP) 5-A, Lyphochek Diabetes Controls (Bio-Rad Laboratories, USA) are used for precision. Two (low and high) levels of quality control materials were analyzed twice a day for 20 days, after which the mean, total standard deviation (SD) and total coefficient of variation (CV), including the between-run CV and between-day CV were calculated. ARKRAY ADAMS HA-8180 HbA1c analyzer and Variant II Turbo were compared with 150 samples according to CLSI EP9-A2. In addition, the linearity and carry over rate were evaluated. Results: Between-run CVs for low and high level quality control materials were 0.0% and 0.3%, respectively, whereas between-day CVs for low and high level quality control materials were 0.3% and 0.2%, respectively. In the linearity test, the coefficient of determination (R) was 0.99 (range, 3.1-19.3%). Thus, a good correlation was observed between ARKRAY ADAMS HA-8180 HbA1c analyzer and Variant II Turbo (R=0.994). The carry over rate was 0.0%. Conclusions: The ARKRAY ADAMS HA-8180 HbA1c analyzer showed excellent precision, linearity, and carryover rate. It also showed excellent correlation with the NGSP certified Variant II Turbo. In conclusion, the ARKRAY ADAMS HA-8180 HbA1c analyzer is a reliable high-performance liquid chromatography (HPLC) analyzer for HbA1c analysis and could be very useful for the diagnosis, treatment, monitoring, and risk assessment of diabetes.

Performance Characteristics of a New Levetiracetam Immunoassay and Method Comparison With a High-Performance Liquid Chromatography Method

Although levetiracetam is recognized for ease of dosing and being well tolerated, therapeutic drug monitoring is potentially useful in certain clinical situations. High-performance liquid chromatography has been commonly used for measuring levetiracetam. Recently, a homogeneous immunoassay for levetiracetam measurement in serum and plasma was introduced by ARK Diagnostics, Inc. The goal of this work was to validate this assay on a random access instrument. This immunoassay was established on the Siemens ADVIA 1200 automated chemistry analyzer. The intraday precision was assessed by 10 replicates of two levels of quality control materials in a batch, whereas interday precision was estimated by assaying the same materials one set per day for 20 days. Linearity was evaluated by serially diluting the highest calibrator and a high patient specimen run in triplicate, whereas the lower limit of quantification was confirmed by 10 measurements of a low-level specimen diluted from a calibrator and another from a diluted patient specimen. This method was compared with a commercial high-performance liquid chromatography method (Chromsystems) using 63 specimens from patients who were on levetiracetam therapy. The assay cycle was 10 minutes with a theoretical throughput of 800 per hour. The intra- (n = 10) and interday (n = 20) coefficients of variation were 8.1% or less for the two levels tested. The manufacturer-claimed analytical measurable range (2.0-100.0 μg/mL) was confirmed by serial dilution and lower limit of quantification experiments. Among the 63 patient samples studies, four showed levetiracetam levels below 2.0 μg/mL by both methods. Deming regression using the remaining 59 paired patient results by ARK immunoassay and the high-performance liquid chromatography method showed a correlation coefficient of 0.9962, a linear regression slope of 0.98, and an intercept of 0.61 with a mean bias of 0.04%. The ARK immunoassay is suitable for clinical use of monitoring levetiracetam levels in serum/plasma on an automated chemistry analyzer (Siemens ADVIA 1200).

METHOD VALIDATION STUDY TO EVALUATE THE ANALYTICAL PERFORMANCE OF THE STAT–SITE METER FOR THE MEASURMENT OF SERUM BETA-HYDROXYBUTRATE

Objectives: To evaluate the analytical performance of the STAT-Site meter (Stanbio laboratory USA) for the measurement of serum beta-hydroxybutyrate (? OH-B) concentration. Methods: The precision was evaluated using two levels of quality control materials (low and high). Within run and between run precision studies were performed. CVs (coefficient of variation) compared against accepted standards. Fifty-one leftover patient samples with previously reported ? OH-B concentrations were used for the method comparison. The accuracy was evaluated and compared to our current laboratory method, (Wako Autokit 3-HB, Wako chemical USA). Slope, intercept, correlation coefficient, Deming regression and paired t-test were calculated using Analyse-it® software Results: The meter showed reasonable precision for the measurement of ? OH-B with CV of 0.0% and 6% for within run precision study and 8.82% and 10.07% for between run precision study which are acceptable according to two CAP surveys. Further these are comparable to our current method CV and the manufacturer claimed CV’s. Deming regression analysis showed a linear relationship between the two methods: The slope of the regression equation was 0.98 (95% CI, 0.87-1.08); intercept 0.10 (95% CI 0.03-0.16) and correlation coefficient of 0.979.There was no bias detected by the visual inspection of the difference plot, this was confirmed by the calculation of the paired t-test (p = 0.19). Conclusion: The STAT-Site meter is a practical, rapid method with wide analytical range that meets precision and accuracy criteria. The method is suitable for the use in a research context until it gets approval for clinical use.

Performance characteristics of seven automated thyroxine and T-uptake methods

BackgroundEstimates of the free thyroxine concentration can be made using measurements of thyroxine (T4) and the thyroid hormone binding ratio (THBR, usually reported as T-uptake) according to the formula free thyroxine index (FTI)=T4×THBR. We evaluated the performance characteristics of 7 pairs of automated T4 and T-uptake methods. MethodsWe evaluated the Architect i2000, AxSYM, ADVIA Centaur, UniCel DxI 800, Immulite 2000, Modular E170 and Vitros ECi methods for T4 and T-uptake. Imprecision was assessed by duplicate determinations on 3 levels of quality control material per run, 2 runs per day, on 5 separate days. Method comparison studies were performed with 205 patient samples and 68 samples from subjects in the second or third trimester of pregnancy. Results for both imprecision and method comparison were converted to the THBR as outlined by each method's manufacturer. ResultsOverall CVs for T4 and THBR methods were 3.2–8.9% and 1.2–6.7%, respectively. T4 methods generally agreed well. The THBR methods did not agree nearly as well. Comparison of FTI results with free T4 by equilibrium dialysis showed good correlation but different slopes. ConclusionsAll methods show adequate precision but the THBR and FTI results are not well standardized.

Performance characteristics of five automated serum cortisol immunoassays

Background: Serum cortisol measurements are used to help diagnose conditions of cortisol deficiency and excess. Automated, nonisotopic immunoassays are used in most clinical laboratories. Methods: Linearity, imprecision, and method comparison studies for serum cortisol assays were performed with the Access®, Advia Centaur®, AxSYM®, Elecsys® 2010, and IMMULITE® 2000 analyzers. Results: All methods demonstrated acceptable linearity with the AxSYM method showing the least deviation from target values. The Elecsys 2010 method was the most precise for all three levels of quality control material. Method comparison studies demonstrated good concordance among methods except for two patient samples that gave results on the Elecsys 2010 that were significantly higher than the other methods. Differences in assay calibration were observed. Conclusions: Overall, all methods performed well. Additional calibration standardization efforts are required to truly harmonize the results from each assay. The Elecsys 2010 method is less specific than other automated methods based on two discordant patient results.