Verification of the Performance of a Fully Automated Coagulation Analyzer and Ongoing Assessment of External Quality Assurance Results in an Academic Laboratory in South Africa.

BACKGROUND: Verification of the performance of analytical platforms is indicated prior to adoption of new Technology for patient sample analysis. Acceptance criteria for the performance of coagulation analytical platforms are not always readily available and is complicated by the multiple assays and test principles in this section of the clinical laboratory. Coagulation samples are also prone to pre-analytical, post-sample collection variables potentially interfering with accuracy analysis. METHODS: This verification study assessed the accuracy of the automated STAGO STA-R Max® coagulation analyzers by means of a comparison study of results obtained on the previously validated STAGO STA-R Evolution® analyzer for 22 coagulation parameters on 40 individual patient samples for each parameter. Within- and between- run reproducibility on commercial control material, carry-over from abnormal to normal samples and the interference of bilirubin, hemoglobin and lipids on the chromogenic analytical channel were also assessed. Ongoing evaluation of the analyzer performance was assessed by External Quality Assurance (EQA) scheme participation. RESULTS: The reproducibility (precision) on 2 levels (Normal and Pathological) commercial control material was acceptable with co-efficient of variance (CV) results below the manufacturer target % CVs. The correlation study demonstrated accuracy of results obtained on the analyzers for all parameters except for D-dimers and coagulation Factor VII. Subsequent EQA performance for these two parameters were however satisfactory. Interference from bilirubin, hemoglobin and lipids did occur in the chromogenic channel. No clinically significant carry over from abnormal to normal samples were observed. CONCLUSIONS: The performance of the STAGO STA-R Max® analyzer is acceptable across the full coagulation test repertoire with the exception of the von Willebrand activity assay. Participation in EQA scheme assessments will be an integral part of ongoing monitoring of the performance of this automated analyzer.

Analytical Performance of a New Immunoturbidimetric Assay for von Willebrand Factor (VWF) Activity Testing.

BACKGROUND: Von Willebrand disease requires laboratory confirmation with quantitative and qualitative measurements of von Willebrand factor (VWF). Qualitative VWF-activity (VWF-Ac) tests have poor inter- and intra-laboratory reproducibility with coefficients of variation (CVs) as high as 64%, often lacking accuracy at low VWF-Ac levels. METHODS: This study evaluated the recently launched immunoturbidometric STAGO® STA-VWF:RCo® reagent for VWF-Ac. Accuracy was evaluated on 32 samples by comparing results using the Siemens® Innovance® reagent. An intra-run reproducibility study was performed on controls. Linearity and lower limit of detection was studied on external-quality-assurance (EQA) material with a known VWF-Ac level. RESULTS: STA-VWF:RCo® reagent results were within clinical interpretation agreement with Siemens® Innovance®. The reproducibility study yielded % CVs of 8.41 for normal and 11.46 for abnormal controls and the assay was linear between 73 and 14.6% and remained linear to 2% with extrapolation. CONCLUSIONS: The STAGO® STA-VWF:RCo® reagent showed clinically meaningful accuracy and acceptable precision.

Integrity of Uncapped Routine Coagulation Specimens Processed in an Automated Integrated Laboratory.

BACKGROUND: The validity of laboratory results depends on pre-analytical variables not detected by conventional quality control. Recommendations are for post-centrifugation coagulation samples to remain capped with cappiercing primary tube analysis. Total laboratory automation integrates analytical platforms with potential incompatibilities necessitating changes including pre-analytical uncapping of samples. METHODS: Samples analyzed for Prothrombin Time (PT), activated Partial Thromboplastin Time (aPTT), D-dimers, Antithrombin and Fibrinogen at baseline, and after 60 and 120 minutes were left at ambient temperature, either re-capped or uncapped, in order to simulate changes from baseline that could occur in uncapped samples on an automation track prior to analysis. Changes were compared to the maximal permissible bias. RESULTS: Sample uncapping for up to 120 minutes at ambient temperature post-centrifugation did not result in clinically significant changes in routine coagulation parameters. CONCLUSIONS: Routine coagulation parameters will not change significantly if the primary citrate tubes are uncapped after centrifugation prior to analysis.

Non-invasive prenatal testing for fetal chromosomal abnormalities by low-coverage whole-genome sequencing of maternal plasma DNA: review of 1982 consecutive cases in a single center.

OBJECTIVE: To review the performance of non-invasive prenatal testing (NIPT) by low-coverage whole-genome sequencing of maternal plasma DNA at a single center. METHODS: The NIPT result and pregnancy outcome of 1982 consecutive cases were reviewed. NIPT was based on low coverage (0.1×) whole-genome sequencing of maternal plasma DNA. All subjects were contacted for pregnancy and fetal outcome. RESULTS: Of the 1982 NIPT tests, a repeat blood sample was required in 23 (1.16%). In one case, a conclusive report could not be issued, probably because of an abnormal vanished twin fetus. NIPT was positive for common trisomies in 29 cases (23 were trisomy 21, four were trisomy 18 and two were trisomy 13); all were confirmed by prenatal karyotyping (specificity=100%). In addition, 11 cases were positive for sex-chromosomal abnormalities (SCA), and nine cases were positive for other aneuploidies or deletion/duplication. Fourteen of these 20 subjects agreed to undergo further investigations, and the abnormality was found to be of fetal origin in seven, confined placental mosaicism (CPM) in four, of maternal origin in two and not confirmed in one. Overall, 85.7% of the NIPT-suspected SCA were of fetal origin, and 66.7% of the other abnormalities were caused by CPM. Two of the six cases suspected or confirmed to have CPM were complicated by early-onset growth restriction requiring delivery before 34 weeks. Fetal outcome of the NIPT-negative cases was ascertained in 1645 (85.15%). Three chromosomal abnormalities were not detected by NIPT, including one case each of a balanced translocation, unbalanced translocation and triploidy. There were no known false negatives involving the common trisomies (sensitivity=100%). CONCLUSIONS: Low-coverage whole-genome sequencing of maternal plasma DNA was highly accurate in detecting common trisomies. It also enabled the detection of other aneuploidies and structural chromosomal abnormalities with high positive predictive value.

Tardive dyskinesia and positive and negative symptoms of schizophrenia. A study using instrumental measures.

BACKGROUND: Controversy surrounds the relationship between tardive dyskinesia (TD) and symptoms of schizophrenia. While some studies reported that negative symptoms of schizophrenia may be a risk factor for TD, others reported a relationship between TD and positive symptoms. METHOD: Eighty-four patients were studied, of whom 47 met criteria for TD. Clinical and instrumental procedures were used to increase the sensitivity of our assessments of the presence and severity of TD. Stepwise logistic and linear regression procedures were used to identify demographic variables, psychopathology, and motor parameters associated with the presence and severity of TD. RESULTS: A 3-factor model consisting of age, clinical tremor, and negative symptoms explained 25% of the variance in clinical TD severity. A 6-factor model consisting of female gender, instrumental and clinical measures of parkinsonism, positive, and negative symptoms explained 49% of the variance in severity of instrumentally derived dyskinesia. CONCLUSIONS: These results suggest that the presence of TD may be associated with positive symptoms; that the severity of TD may be related to negative symptoms; and that the relationship between negative symptoms and TD severity may be influenced by the presence of parkinsonism.