International organizations require from medical laboratories a quantitative statement of the uncertainty in measurement (UM) to help interpret patient results. The French accreditation body (COFRAC) ...recommends an approach (SH GTA 14 IQC/EQA method) using both internal quality control (IQC) and external quality assessment (EQA) data. The aim of this work was to validate an alternative way to quantify UM using only EQA results without any need for IQC data. This simple and practical method, which has already been described as the long-term evaluation of the UM (LTUM), is based on linear regression between data obtained by participants in EQA schemes and target values. We used it for 43 routine analytes covering biochemistry, immunoassay, and hemostasis fields.
Data from 50 laboratories participating in ProBioQual (PBQ) EQA schemes over 25 months were used to obtain estimates of the median and 90th percentile LTUM and to compare them to the usual analytical goals. Then, the two UM estimation methods were compared using data from 20 laboratories participating in both IQC and EQA schemes.
Median LTUMs ranged from 2.9% (sodium) to 16.3% (bicarbonates) for biochemistry analytes, from 12.6% (prothrombin time) to 18.4% (factor V) for hemostasis analytes when using the mean of all participants, and were around 10% for immunoassays when using the peer-group mean. Median LTUMs were, in most cases, slightly lower than those obtained with the SH GTA 14 method, whatever the concentration level.
LTUM is a simple and convenient method that gives UM estimates that are reliable and comparable to those of recommended methods. Therefore, proficiency testing (PT) organizers are allowed to provide participants with an additional UM estimate using only EQA data and which could be updated at the end of each survey.
Summary
Acquired factor V inhibitor (AFVI) is an extremely rare disorder that may cause severe bleeding. To identify factors associated with bleeding risk in AFVI patients, a national, multicentre, ...retrospective study was made including all AFVI patients followed in 21 centres in France between 1988 and 2015. All patients had an isolated factor V (FV) deficiency <50% associated with inhibitor activity. Patients with constitutional FV deficiency and other causes of acquired coagulation FV deficiencies were excluded. The primary outcome was incident bleeding and factors associated with the primary outcome were identified. Thirty‐eight (74 36–100 years, 42·1% females) patients with AFVI were analysed. Bleeding was reported in 18 (47·4%) patients at diagnosis and in three (7·9%) during follow‐up (7 0·2–48.7 months). At diagnosis, FV was <10% in 31 (81·6%) patients. Bleeding at diagnosis was associated with a prolonged prothrombin time that strongly correlated with the AFVI level measured in plasma {r = 0·63, 95% confidence interval (CI) 0·36–0·80, P < 0·05}. Bleeding onset during follow‐up was associated with a slow AFVI clearance (P < 0·001). The corresponding receiver operating characteristics curve showed that AFVI clearance was predictive of bleeding onset with an AFVI clearance of seven months with a sensitivity of 100% (95% CI: 29–100) and a specificity of 86% (95% CI: 57–98, P = 0·02). Kaplan–Meier analysis showed that AFVI clearance >7 months increased the risk of bleeding by 8 (95% CI: 0·67–97, P = 0·075). Prothrombin time at diagnosis and time for clearance of FV inhibitor during follow‐up are both associated with bleeding in patients with AFVI.
Dabigatran etexilate, rivaroxaban and apixaban (DOACs) are widely used and measurement of their concentration is desirable in certain clinical situations. Target-specific assays are available but ...limited information exists on their performance especially in their ability to accurately measure low and high concentrations.
To define, in a multicenter study, the precision and accuracy of DOAC measurements in daily practice.
15 plasma samples (kindly provided by Hyphen-Biomed) spiked with 5 blinded concentrations of dabigatran, rivaroxaban or apixaban (targeted 0–40–100–250–500ng/mL, actual concentrations measured by HPLC-MS/MS), were sent to 30 haemostasis laboratories. DOAC concentration, PT and aPTT were measured once in each sample using local reagents. Interlaboratory precision was determined by its coefficient of variation (CV) and accuracy by its bias.
464 DOAC measurements were performed in the 30 laboratories using 4 dabigatran and 5 rivaroxaban/apixaban calibrated assays on 3 analysers. Inter-laboratory CVs were below 18% for concentrations ≥100ng/mL, and higher for concentrations ~40ng/mL; biases were below 8% for all drugs and concentrations. In DOAC-free samples, concentrations were all below the lower limit of quantification except for one value (dabigatran: 35ng/mL). Depending on the concentrations, significant differences were found between reagents in rivaroxaban and apixaban concentration values. PT and aPTT ratios displayed a low sensitivity to apixaban.
Our results suggest that calibrated DOAC assays allow the reliable measurement of a wide range of drug concentrations, even though improvement of their performances is necessary, especially for measuring low concentrations.
•Information on the performances of direct oral anticoagulants (DOAC) assays are required.•A wide range of DOAC concentrations were tested in a multicenter study (30 laboratories).•Good accuracy and acceptable precision of DOAC commercial assays were found.•Improvements are necessary for measuring low DOAC concentrations.•PT or aPTT are unable to detect low concentrations of rivaroxaban and dabigatran and “on-therapy” concentrations of apixaban.
: Laboratory quality programs rely on internal quality control and external quality assessment (EQA). EQA programs provide unknown specimens for the laboratory to test. The laboratory's result is ...compared with other (peer) laboratories performing the same test. EQA programs assign target values using a variety of methods statistical tools and performance assessment of 'pass' or 'fail' is made. EQA provider members of the international organization, external quality assurance in thrombosis and hemostasis, took part in a study to compare outcome of performance analysis using the same data set of laboratory results. Eleven EQA organizations using eight different analytical approaches participated. Data for a normal and prolonged activated partial thromboplastin time (aPTT) and a normal and reduced factor VIII (FVIII) from 218 laboratories were sent to the EQA providers who analyzed the data set using their method of evaluation for aPTT and FVIII, determining the performance for each laboratory record in the data set. Providers also summarized their statistical approach to assignment of target values and laboratory performance. Each laboratory record in the data set was graded pass/fail by all EQA providers for each of the four analytes. There was a lack of agreement of pass/fail grading among EQA programs. Discordance in the grading was 17.9 and 11% of normal and prolonged aPTT results, respectively, and 20.2 and 17.4% of normal and reduced FVIII results, respectively. All EQA programs in this study employed statistical methods compliant with the International Standardization Organization (ISO), ISO 13528, yet the evaluation of laboratory results for all four analytes showed remarkable grading discordance.
Severe hemophilia A is an X-linked bleeding disorder. Immune tolerance induction (ITI) is the best strategy of treatment when patients develop inhibitors. The objective is to illustrate the benefit ...of a high-purity human factor VIII/von Willebrand factor (VWF) concentrate (Octanate) in the management of ITI. We also wanted to raise the potential interest of laboratory assays such as thrombin-generation test (TGT) and epitope mapping. Two patients were treated during ITI, first with a recombinant FVIII and then with plasma-derived factor VIII without success, and, finally, with Octanate. Bypassing agents were used based on the results of TGT. Epitope mapping was performed during ITI therapy. These observations suggest the potential contribution of Octanate in the management of ITI in difficult cases. The use of bypassing agents can be necessary in prophylaxis or to treat bleedings, and may be guided by TGT results. Epitope mapping is used to describe the inhibitor. This article shows a decrease of the inhibitor directed against the C2 domain after initiation of Octanate. A high-purity human factor VIII/von Willebrand factor concentrate (Octanate) may be a valuable therapeutical option for ITI therapy. TGT and epitope mapping could be of help in the management of ITI.
Deletions in the β-globin locus control region (β-LCR) lead to ( γδβ)0-thalassemia ( γδβ)0-thal. In patients suffering from these rare deletions, a normal hemoglobin (Hb), phenotype is found, ...contrasting with a hematological thalassemic phenotype. Multiplex-ligation probe amplification (MLPA) is an efficient tool to detect β-LCR deletions combined with long-range polymerase chain reaction (PCR) and DNA sequencing to pinpoint deletion breakpoints. We present here a novel 11,155 bp β-LCR deletion found in a French Caucasian patient which removes DNase I hypersensitive site 2 (HS2) to HS4 of the β-LCR. Interestingly, a 197 bp insertion of two inverted sequences issued from the HS2-HS3 inter-region is present and suggests a complex rearrangement during replication. Carriers of this type of thalassemia can be misdiagnosed as an α-thal trait. Consequently, a complete α- and β-globin gene cluster analysis is required to prevent a potentially damaging misdiagnosis in genetic counselling.
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