International collaborative study for the calibration of proposed International Standards for thromboplastin, rabbit, plain, and for thromboplastin, recombinant, human, plain.

Essentials Two candidate International Standards for thromboplastin (coded RBT/16 and rTF/16) are proposed. International Sensitivity Index (ISI) of proposed standards was assessed in a 20-centre study. The mean ISI for RBT/16 was 1.21 with a between-centre coefficient of variation of 4.6%. The mean ISI for rTF/16 was 1.11 with a between-centre coefficient of variation of 5.7%. SUMMARY: Background The availability of International Standards for thromboplastin is essential for the calibration of routine reagents and hence the calculation of the International Normalized Ratio (INR). Stocks of the current Fourth International Standards are running low. Candidate replacement materials have been prepared. This article describes the calibration of the proposed Fifth International Standards for thromboplastin, rabbit, plain (coded RBT/16) and for thromboplastin, recombinant, human, plain (coded rTF/16). Methods An international collaborative study was carried out for the assignment of International Sensitivity Indexes (ISIs) to the candidate materials, according to the World Health Organization (WHO) guidelines for thromboplastins and plasma used to control oral anticoagulant therapy with vitamin K antagonists. Results Results were obtained from 20 laboratories. In several cases, deviations from the ISI calibration model were observed, but the average INR deviation attributabled to the model was not greater than 10%. Only valid ISI assessments were used to calculate the mean ISI for each candidate. The mean ISI for RBT/16 was 1.21 (between-laboratory coefficient of variation [CV]: 4.6%), and the mean ISI for rTF/16 was 1.11 (between-laboratory CV: 5.7%). Conclusions The between-laboratory variation of the ISI for candidate material RBT/16 was similar to that of the Fourth International Standard (RBT/05), and the between-laboratory variation of the ISI for candidate material rTF/16 was slightly higher than that of the Fourth International Standard (rTF/09). The candidate materials have been accepted by WHO as the Fifth International Standards for thromboplastin, rabbit plain, and thromboplastin, recombinant, human, plain.

Performance evaluation of the automated nucleated red blood cell enumeration on Sysmex XN analyser.

INTRODUCTION: Presence of peripheral blood nucleated red blood cell (NRBC) is associated with pathological conditions and leads to the overestimation of white blood cell count in automated haematology analysers (HA). The authors evaluated NRBC enumeration by a new HA Sysmex XN (XN) to demonstrate the precision and comparability to manual count (MC) at the various NRBC values. METHODS: Specimens with initially NRBC positive were included. For precision assessment, 8 levels of NRBCs were repeatedly analysed. For comparison study, 234 specimens were analysed by both XN and MC. RESULTS: For precision study, the percentage of coefficient of variation ranged from 14% to 45.6% and 1.2% to 4.4% for MC and XN, respectively. For comparison study between XN and MC, NRBCs ranged from 0% to 612.5%. Regression analysis demonstrated an r(2) of 0.98. The mean bias of 14.1% with 95% limits of agreement between -48.76% and 76.95% was found. The NRBC counts from XN appeared to be more in accordance with MC when the NRBCs were lower than 200% with the concordance rate of 94.2%. CONCLUSION: The automated NRBC enumeration by XN was precise and could replace the traditional MC, especially for the specimens with NRBCs lower than 200%.

Current practices of bleeding time in a developing country: an alert for noncompliance with the standard procedures.

INTRODUCTION: Bleeding time is still widely performed in many developing countries including Thailand. To generate an accurate result, the procedure should be complied with standard recommendations such as those from Clinical and Laboratory Standards Institute (CLSI) and World Federation of Hemophilia (WFH). The authors surveyed the current practices of bleeding time in Thailand in order to verify the practices that did not comply with the accepted standard. METHODS: The questionnaires were sent to hospitals participating Thailand National External Quality Assessment Scheme (NEQAS) for blood coagulation. Items in the questionnaire comprised information about preanalytical, analytical, and postanalytical issues of bleeding time. RESULTS: From a dispatch of 201 questionnaires, 155 (77.1%) were returned. The common noncompliance with standards observed in this survey included inappropriateness of indication, e.g. use for preoperative screening (95 of 126, 75.4%), use of devices other than standard template (130 of 132, 98.5%), and inappropriate reference range (125 of 127, 98.4%). CONCLUSIONS: The noncompliance shown in this survey can affect the accuracy of bleeding time results. The authors would like to address these problems as an alert for other laboratories especially in the developing countries where the standard templates are not widely available.

Evaluation of Thrombi-Stat MC1 for whole blood and plasma international normalized ratio in comparison with a laboratory method.

INTRODUCTION: The precision and comparability of the international normalized ratio (INR) analyzed by the Thrombi-Stat MC1 coagulation testing system were evaluated before using as a point-of-care testing. METHODS: Three levels of control materials were used for within-run and between-run precision study. Comparison study of INR determination from citrated whole blood (INR-WB) and citrated plasma (INR-PL) analyzed by the Thrombi-Stat MC1 with those by the validated method, Sysmex® CS-2100i (INR-CS), was performed. RESULTS: The within-run coefficient of variations (CVs) of INR by the Thrombi-Stat MC1 were 3.60% to 4.80%. For between-run precision, the CVs were 4.26 to 4.93%. Fifty-four plasmas from patients receiving warfarin were included for comparability testing. There were good correlation and agreement between both INR-WB and INR-PL compared with INR-CS. Eighty-seven percent of INR-WB and 100% of INR-PL were within ± 0.5 units of the INR-CS. Given that the therapeutic range was INR-CS of 2-3, 3.7% of INR-WB and 5.56% of INR-PL were discordant with the INR-CS. CONCLUSION: The precision and comparability to validated method of the Thrombi-Stat MC1 were acceptable. Either citrated whole blood or plasma may be used as samples in this system. Impact on the management of patients must be taken into consideration prior to the implementation of this system.