Review of coagulation preanalytical variables with update on the effect of direct oral anticoagulants

There are many preanalytical variables (PAV) that are known to affect coagulation testing. The more commonly acknowledged PAV addressed by the clinical laboratory tend to start with their influence on blood collection, but realistically coagulation PAV starts with the patient, where the laboratory has less influence or control. Patient selection and appropriate timing for blood collection may be integral for assuring proper diagnosis and management. Laboratory control and assurance for ideal phlebotomy practice would mitigate most PAVs related to blood collection to minimize suboptimal sample collection. Laboratory oversight of sample transportation, processing and storage will assure sample integrity until testing can be facilitated. The purpose of this document is to review common PAV that should be taken into consideration when ordering, performing and interpreting a coagulation test result, with additional attention to the effect of direct oral anticoagulants (DOACs).     

Impact of evacuated collection tube fill volume and mixing on routine coagulation testing using 2.5-ml (pediatric) tubes

BACKGROUND: Anecdotal observations by pharmacists monitoring anticoagulated patients indicate that blood samples collected in 2.7-mL (pediatric) evacuated tubes frequently produced falsely elevated international normalized ratio (INR) results. OBJECTIVE: To evaluate the impact of various preanalytical variables (fill volume, sample mixing, and elapsed time between sample collection and mixing) on INR test results using pediatric collection tubes in healthy volunteers and patients receiving warfarin anticoagulation therapy. Fifteen patients receiving warfarin and the 15 healthy volunteers participated in each study arm. METHODS: Multiple blood samples for coagulation testing were obtained from study subjects in full-draw pediatric collection tubes made of siliconized glass. The impact of sample mixing was evaluated by randomly varying the number of times each tube (five tubes total) was inverted following sample collection between one and five. The impact of timely sample mixing was evaluated by randomly varying the elapsed time between sample collection and mixing between 0 min and 4 min in each of five samples. The impact of incomplete collection tube filling was evaluated by randomly varying the volume of six tubes between 50% and 100%. Duplicate coagulation assays were performed on each sample by a centralized hematology laboratory, and the average result was reported. RESULTS: Statistical analysis revealed that neither sample mixing nor the elapsed time between sample collection and mixing had a statistically significant effect on INR test results. For patients receiving warfarin, tube fill volume had a statistically significant effect on the reported INR results (p < 0.001). The mean (+/- SD) INR derived from sample tubes filled 100% was 3.2 +/- 1.2, compared to 9.9 +/- 4.2 for tubes filled only 50% full (p < 0.01). Statistically significant INR elevations became apparent for sample tube fill volumes of < 90%. CONCLUSION: Pediatric blood collection tubes should be filled at least 90% full to ensure accurate INR test results. Anticoagulation therapy providers should routinely inquire about the type of collection tube used (adult vs pediatric) and the adequacy of sample collection volume before deriving therapeutic plans in asymptomatic excessively anticoagulated patients.     

Routine Coagulation Testing: Do We Need a Discard Tube?

When coagulation tests are performed, the recommended guideline is that a discard tube be used and the coagulation testing should be done only on the second tube. This guideline is however inconsistently enforced and most laboratories follow a single tube draw for routine coagulation testing. Few studies have however, challenged this guideline and have shown that comparable results can be obtained in both tubes when a two tube draw is used. This prospective study was done over a 3 months period in the hematology laboratory under the Clinical Hematology unit of a tertiary care teaching institution in North India. Fifty-six paired specimens were drawn from healthy volunteers following the prescribed “two tube draw” method. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were performed within 1 h of sample collection on a fully automated photo-optical coagulation instrument (Ceveron-Alpha). Paired results for PT and APTT were compared using Bland–Altman plots for method comparison. There was good correlation between the PT, INR and APTT of the first and second tubes with bias of 0.09, −0.05 and 0.3 respectively). Bland–Altman plots showed acceptable agreement between the two values with 95 % confidence interval ranging from −0.62 to 0.79 for PT, −0.05 to 0.06 for INR and −3.9 to 4.6 for APTT. Our study has shown no significant difference between PT and APTT values for the first and second tubes. Hence the use of a discard tube is not required.     

Thrombin Generation During Collection and Storage of Blood

Thrombin generation, as evidenced by radioimmunologic fibrinopeptide A (FPA) determination, was studied upon drawing and storage of blood. Blood from 5 healthy subjects was drawn into Fenwal bags (PL 146, 16-gauge needle, 92-cm collecting tube), and blood samples for FPA analysis were taken from the proximal and distal part of the collecting tubes. The FPA concentrations were considerably higher in the distal part of the tubes both at zero time and after 5 and 10 min, implying substantial thrombin generation to have occurred upon blood passing through the tubes. In 20 healthy blood donors (age 19-52 years) subjected to a standard collection procedure (Fenwal bags PL 146, CPDA formula-1 anticoagulant solution, 450 ml blood), higher FPA values were observed in the bags immediately upon collection, as compared to control venipuncture values (p less than 0.02). Furthermore, in 6 women using oral contraceptives, even larger increases were observed, indicating thrombin generation to be more pronounced in such donors (p less than 0.01). No statistically significant increase in FPA concentrations was found upon storage of CPDA-blood at 4 degrees C for 24 h. There was no correlation between FPA and beta-thromboglobulin (BTG) concentrations after blood collection, indicating alpha-granule release from platelets to be non-thrombin-mediated.     

Influence of the centrifuge time of primary plasma tubes on routine coagulation testing.

Preparation of blood specimens is a major bottleneck in the laboratory throughput. Reliable strategies for reducing the time required for specimen processing without affecting quality should be acknowledged, especially for laboratories performing stat analyses. The present investigation was planned to establish a minimal suitable centrifuge time for primary samples collected for routine coagulation testing. Five sequential primary vacuum tubes containing 0.109 mol/l buffered trisodium citrate were collected from 10 volunteers and were immediately centrifuged on a conventional centrifuge at 1500 x g, at room temperature for 1, 2, 5, 10 and 15 min, respectively. Hematological and routine coagulation testing, including prothrombin time, activated partial thromboplastin time and fibrinogen, were performed. The centrifugation time was inversely associated with residual blood cell elements in plasma, especially platelets. Statistically significant variations from the reference 15-min centrifuge specimens were observed for fibrinogen in samples centrifuged for 5 min at most and for the activated partial thromboplastin time in samples centrifuged for 2 min at most. Meaningful biases related to the desirable bias were observed for fibrinogen in samples centrifuged for 2 min at most, and for the activated partial thromboplastin time in samples centrifuged for 1 min at most. According to our experimental conditions, a 5-10 min centrifuge time at 1500 x g may be suitable for primary tubes collected for routine coagulation testing.     

Quality and reliability of routine coagulation testing: can we trust that sample?

Poor standardization of preanalytic variables exerts a strong influence on the reliability of coagulation testing, consuming valuable health care resources and compromising patient outcome. Most uncertainties emerge from patient misidentification and the procedures for specimen collection and handling. Location of unsuitable venous access or problematic phlebotomies may produce spurious activation of the hemostatic system and hemolytic specimens. Prolonged venous stasis is associated with hemoconcentration and spurious variations of most coagulation assays. Additional pitfalls can be introduced by inappropriate phlebotomy tools and small-gauge needles. Inappropriate filling and mixing of the tube, unsuitable procedures for centrifugation and storage of the specimens are additional aspects that need accurate standardization. Besides traditional preanalytic variables affecting routine coagulation testing, thrombin-generation assays require specific criteria to be accurately fulfilled. These aspects include the type of specimen (platelet-poor plasma, platelet-rich plasma or whole blood), blood collection tubes, storage conditions and the presence of residual platelets. Compliance with new international quality assessment programs, which will also involve coagulation laboratories, encompasses the adoption of suitable strategies for reducing undue variability throughout the whole testing process. Such strategies would not entail extraordinary costs and are affordable with a structured outlay of existing resources, educational policies and compliance with reliable guidelines.     

International Council for Standardization in Haematology (ICSH) recommendations for processing of blood samples for coagulation testing

This guidance document has been prepared on behalf of the International Council for Standardization in Haematology (ICSH). The aim of the document is to provide guidance and recommendations for the processing of citrated blood samples for coagulation tests in clinical laboratories in all regions of the world. The following areas are included in this document: Sample transport including use of pneumatic tubes systems; clots in citrated samples; centrifugation; primary tube storage and stability; interfering substances including haemolysis, icterus and lipaemia; secondary aliquots—transport, storage and processing; preanalytical variables for platelet function testing. The following areas are excluded from this document, but are included in an associated ICSH document addressing collection of samples for coagulation tests in clinical laboratories; ordering tests; sample collection tube and anticoagulant; preparation of the patient; sample collection device; venous stasis before sample collection; order of draw when different sample types are collected; sample labelling; blood-to-anticoagulant ratio (tube filling); influence of haematocrit. The recommendations are based on published data in peer-reviewed literature and expert opinion.     

The sensitivity and specificity of a red blood cell agglutination D-dimer assay for venous thromboembolism when performed on venous blood.

BACKGROUND: Studies evaluating the accuracy of the SimpliRED D-dimer assay for venous thromboembolism (VTE) have used a capillary fingerstick blood sample, which requires the test to be performed immediately at the bedside. Initial studies showed a sensitivity for VTE of 90% to 95% when the assay was performed by a finite number of experienced health care workers. However, because of the test's subjectivity, misinterpretation of the result is possible when performed by inexperienced staff. Recent reports by other investigators indicated a low sensitivity of this assay for VTE and noted a reduction in sensitivity (84%) for pulmonary embolism. OBJECTIVE: To determine the sensitivity and specificity of the D-dimer test performed in the laboratory by experienced technologists on venous whole-blood samples in routine collection tubes. If D-dimer testing results accurately detect VTE when performed in this manner, concerns about the sensitivity of this assay would be solved. METHODS: One hundred forty-eight consecutive patients with suspected VTE underwent D-dimer testing at the bedside using a fingerstick sample and venous blood collected into a plain tube. Venous blood was also collected into tubes containing tri-potassium EDTA, sodium citrate, or a combination of lithium and heparin for D-dimer testing in the laboratory. In addition, the EDTA tube was refrigerated overnight at 4 degrees C for retesting at approximately 24 hours. The presence or absence of VTE was determined by means of objective results of testing and a 3-month follow-up. RESULTS: Thirty-four subjects (23%) had confirmed VTE (25 with deep vein thrombosis; 9 with pulmonary embolism). All laboratory venous blood D-dimer results showed sensitivities of 97%, specificities of 61% to 64%, and negative predictive values of 99%, compared with 88%, 71%, and 95%, respectively, when the results were obtained by means of fingerstick at the bedside. CONCLUSIONS: The SimpliRED D-dimer assay performed in the laboratory on venous blood, collected into any of 3 routine laboratory tubes, is sensitive and moderately specific for VTE. Based on this study, immediate bedside testing (particularly by inexperienced personnel) under suboptimal conditions is unnecessary. Furthermore, the high sensitivity of refrigerated EDTA samples allows specimens to be stored or transported (on ice at 4 degrees C) for testing for 24 hours after collection.     

Influence of using a roller mixer on rejected samples in coagulation tests

Introduction: The influence of using a roller mixer just after blood collection on the ratio of rejected samples in coagulation tests was investigated retrospectively. Methods: Numbers of blood samples collected in centralized units of outpatient clinics for prothrombin time (PT) were 24 050 in group I and 24 500 in group II (H. Aral, unpublished data). In group I, the tubes were inverted manually. In group II, the tubes were left standing on roller mixer with 30 rpm. The ratios of rejected samples of the two groups were compared statistically with ki‐square analysis. Results: Using a roller mixer, rate of rejection decreased from 0.79% (group I) to 0.20% (group II) (P < 0.001). Conclusion: We suggested using roller mixer to improve the reliability of coagulation testing. Such standardization in preanalytical phase may be helpful in preventing laboratory errors and obtaining correct test results in coagulation tests.     

Time dependent reduction in platelet aggregation using the multiplate analyser and hirudin blood due to platelet clumping

The Multiplate is a popular instrument that measures platelet function using whole blood. Potentially considered a point of care instrument, it is also used by hemostasis laboratories. The instrument is usually utilized to assess antiplatelet medication or as a screen of platelet function. According to the manufacturer, testing should be performed within 0.5–3 hours of blood collection, and preferably using manufacturer provided hirudin tubes. We report time-associated reduction in platelet aggregation using the Multiplate and hirudin blood collection tubes, for all the major employed agonists. Blood for Multiplate analysis was collected into manufacturer supplied hirudin tubes, and 21 consecutive samples assessed using manufacturer supplied agonists (ADP, arachidonic acid, TRAP, collagen and ristocetin), at several time-points post-sample collection within the recommended test time period. Blood was also collected into EDTA as a reference method for platelet counts, with samples collected into sodium citrate and hirudin used for comparative counts. All platelet agonists showed a diminution of response with time. Depending on the agonist, the reduction caused 5–20% and 22–47% of responses initially in the normal reference range to fall below the reference range at 120min and 180min, respectively. Considering any agonist, 35% and 67% of initially “normal” responses became ‘abnormal’ at 120 min and 180 min, respectively. Platelet counts showed generally minimal changes in EDTA blood, but were markedly reduced over time in both citrate and hirudin blood, with up to 40% and 60% reduction, respectively, at 240 min. The presence of platelet clumping (micro-aggregate formation) was also observed in a time dependent manner, especially for hirudin. In conclusion, considering any platelet agonist, around two-thirds of samples can, within the recommended 0.5–3 hour testing window post-blood collection, yield a reduction in platelet aggregation that may lead to a change in interpretation (i.e., normal to reduced). Thus, the stability of Multiplate testing can more realistically be considered as being between 30–120 min of blood collection for samples collected into hirudin.     

Influence of temperature and time before centrifugation of specimens for routine coagulation testing

The accurate standardization of the preanalytical phase is of pivotal importance for achieving reliable results of coagulation tests. Because information on the suitable storage conditions for coagulation testing is controversial, we aimed at investigating the sample stability with regard to the temperature and time before centrifugation. The activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen and D-dimer were assayed in specimens collected from 26 consecutive patients on antivitamin K therapy on the ACL TOP analyzer. Three primary 3.6-ml siliconized evacuated tubes containing 0.109 mol/l buffered trisodium citrate were sequentially collected from each patient. These three tubes were mixed, pooled and divided into seven identical aliquots. The first aliquot was immediately centrifuged according to the standard protocol [1500 g for 15 min at room temperature (RT)] and analyzed. The other aliquots were left for 3, 6 and 24 h, respectively, at RT or 4 degrees C, and then centrifuged and analyzed. Test results were compared with those obtained on the reference specimen. Statistically significant prolongations were observed for aPTT in all the samples. Such differences exceeded the analytical quality specifications for desirable bias in the samples stored for 24 h. A significant reduction, yet comprised within the desirable bias, was observed for PT and fibrinogen in uncentrifuged specimens stored at RT for 3 and 6 h. No significant biases could be recorded in D-dimer. In conclusion, a 6-h storage of uncentrifuged specimens at either RT or 4 degrees C may still be suitable to achieve results of routine coagulation testing comprised within the analytical quality specifications for desirable bias.     

Comparison between siliconized evacuated glass and plastic blood collection tubes for prothrombin time and activated partial thromboplastin time assay in normal patients, patients on oral anticoagulant therapy and patients with unfractioned heparin therapy

Introduction: The study was designed to evaluate whether there was a statistically significant effect between evacuated glass tubes and plastic tubes on prothrombin time (PT) and activated partial thromboplastin time (aPTT). Methods: Blood samples were drawn into four different tubes from three patient populations—apparently healthy patients, patients on oral anticoagulant therapy with vitamin K antagonists (OAT‐vka) and patients being treated with unfractioned heparin (UFH). Testing was performed on an automated coagulation analyzer, and statistical analysis was achieved using a test of variance (anova ). Results: For normal patients, there were no statistically significant differences for the aPTT test; however, there were statistically significant differences for the PT test. For patients on OAT‐vka, statistically significant differences were clearly observed between the four tube types for the PT test. For patients treated with UFH, there were no statistically significant differences for the aPTT test. Conclusion: The data showed a statistically significant difference between glass and plastic tubes in the normal population only for the PT test, with consequent repercussions for patients on OAT. This means that appropriate care and validation should take place whenever there is a change in tube type.     

The use of Vacutainer tubes for collection and storage of blood for coagulation testing

Summary. A study has been performed to evaluate the suitability of Vacutainer tubes in blood specimen collection for coagulation tests and to compare them with the conventional syringe technique employed in UK hospitals. Blood was collected from healthy volunteers, an ante-natal group and patients on long-term oral anticoagulants. Samples were stored at two different temperatures; 4|MoC and ambient room temperature (RT). Prothrombin times, factor VII assays and APTT were performed at baseline and after 2 h and 4 h storage. There was significant activation of the extrinsic system in the blood samples collected by Vacutainer when stored at 4|MoC which became more significant on prolonged storage. The effect was less pronounced when the Vacutainer tubes were stored at RT. In contrast, the blood collected by the syringe method did not show these changes with the exception of the ante-natal specimens where a lesser degree of activation than in the Vacutainer tubes was observed after 4 h at 4|MoC. The activation of the Vacutainer samples at 4|MoC is considered undesirable and could be of clinical significance in oral anticoagulant dosage.     

Citrate artificially masks the haemostatic effect of recombinant factor VIIa in dilutional coagulopathy

Most often, thrombelastographic analyses are carried out using citrated blood and re-calcification. However, calcium chelation may affect dynamics of tissue-factor-initiated thrombin generation. The present study investigates the effect of sample anticoagulant on the response of a colloid induced dilutional coagulopathy model to recombinant activated factor VII (rFVIIa) as measured by thrombelastography. Thrombelastographic evaluation of whole blood coagulation activated with minute amounts of tissue factor in a model of in vitro haemodilution with hydroxyethyl starch (HES) 130/0.4 in a prospective laboratory study. Whole blood coagulation was evaluated before and after 30% dilution with HES 130/0.4, and following in vitro addition of rFVIIa to whole blood collected into tubes containing citrate, corn trypsin inhibitor (CTI), and no stabilizers. Haemodilution with HES 130/0.4 induces a coagulopathy characterised by a reduced maximum rate of clot formation and a pronounced reduction in the final clot firmness. With all test mediums investigated, rFVIIa significantly shortened clot initiation phase. In cases of native whole blood and CTI-stabilised whole blood, rFVIIa shortens the clotting time but also demonstrated an acceleration of the maximum velocity of clot formation. When citrate is used as anticoagulants in thrombelastographic clotting assays, these may artificially mask the haemostatic effect of rFVIIa in colloid haemodilution. The effect in vitro of rFVIIa in citrated blood samples may underestimate the haemostatic potential of rFVIIa. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

International Council for Standardisation in Haematology (ICSH) recommendations for collection of blood samples for coagulation testing

This guidance document has been prepared on behalf of the International Council for Standardisation in Haematology (ICSH). The aim of the document is to provide guidance and recommendations for collection of blood samples for coagulation tests in clinical laboratories throughout the world. The following processes will be covered: ordering tests, sample collection tube and anticoagulant, patient preparation, sample collection device, venous stasis before sample collection, order of draw when different sample types need to be collected, sample labelling, blood-to-anticoagulant ratio (tube filling) and influence of haematocrit. The following areas are excluded from this document, but are included in an associated ICSH document addressing processing of samples for coagulation tests in clinical laboratories: sample transport and primary tube sample stability; centrifugation; interfering substances including haemolysis, icterus and lipaemia; secondary aliquots—transport and storage; and preanalytical variables for platelet function testing. The recommendations are based on published data in peer-reviewed literature and expert opinion.     

Prolonged activated partial thromboplastin time in pregnancy: a brief report

BACKGROUND: Limited data are available regarding causes of prolonged activated partial thromboplastin time (aPTT) in otherwise normal pregnancies. We retrospectively evaluated clinical data of pregnant women in whom an elevated aPTT was noted on routine prenatal testing. Our intent was to identify various causes of prolonged aPTT and to evaluate whether the pregnancies were adversely affected. METHODS: A retrospective review of medical records of 36 pregnant patients with a prolonged aPTT as the sole abnormal coagulation test seen in the outpatient department of a tertiary care hospital over a period of 4 years. RESULTS: Patients' median age was 26 (range, 19-41) years and median duration of gestation period was 19 (range, 8-38) weeks. Fifteen patients were primigravida. Of 36 patients, repeated aPTT values were normal in 24 (67%) patients, whereas 12 (33%) patients had persistently elevated aPTT values. Factor XI deficiency was found in 5 patients, lupus anticoagulant in 3 patients, elevated anticardiolipin antibody in 2 patients, and low von Willebrand Factor level in 1 patient. Overall, 23 patients delivered. No patients experienced excessive bleeding or thromboembolism. CONCLUSION: Factor XI deficiency and antiphospholipid antibody were 2 major abnormalities identified in patients with prolonged aPTT. These coagulopathies were not associated with excessive bleeding or thromboembolism. Repeat normal aPTT in approximately 2 thirds of patients suggests that proper sample collection and processing are important for coagulation assays to avoid erroneous clotting times.     

Using a bus service for transporting sputum specimens to the Central Reference Laboratory: effect on the routine TB culture service in Malawi.

SETTING: All non-private hospitals in Malawi that registered TB cases in 2001, during which there was a bus service for transporting sputum specimens to the Central Reference Laboratory (CRL) for mycobacterial culture and drug sensitivity testing (CDST). OBJECTIVES: To determine the performance of the system of collecting and processing sputum specimens from patients with recurrent smear-positive pulmonary TB through to CDST. DESIGN: Structured interviews with TB Officers, and retrospective data collection using TB and laboratory registers. RESULTS: There were 964 patients with recurrent smear-positive PTB. TB Officers took responsibility for collecting and transporting sputum to the CRL, and 73% reported using the bus service. Sputum specimens from 384 (40%) patients arrived at the CRL. Of these, 40% were found to have negative concentrated smears at the CRL, and 36% of specimen sets arriving at CRL were successfully cultured for DST. Most specimens had been collected after the start of anti-tuberculosis treatment. Although delays in collection adversely affected culture, only 43% of specimen sets collected on or before the first day of treatment yielded Mycobacterium tuberculosis. CONCLUSION: Problems were identified at all stages of the system and strategies to remedy these are being put in place.     

Discard first tube for coagulation testing

Tissue thromboplastin may contaminate the first tube sample due to the trauma of the venipuncture, and therefore, affect the accuracy of coagulation testing. This practice was stopped by Clinical and Laboratory Standards Institute after several studies. However, most of the studies have verified these conclusions and refuted the need for a discard tube when drawing samples for coagulation tests in healthy groups. The purpose of our study was to evaluate the clinical importance of discarding a tube for prothrombin time (PT) determinations on large samples with international normalized ratio (INR) values between and over targeted therapeutic range. Patients receiving oral anticoagulation therapy (OAT) managed by our cardiology service were selected for this study. Tube 1 was always treated as the discard tube. Tube 2 was allocated to be analyzed along with the tube 1 for coagulation tests. Individual values were grouped into four cohorts according to the INR range. The ranges were as follows: less than 2.0, 2.1-3.0, 3.1-4.5 and more. Three hundred and seventy-six samples were drawn for PT/INR and activated partial thromboplastin time testing. We found statistically significant differences between tube 1 and tube 2 (P < 0.05), and satisfactory correlation coefficients were obtained by linear regression analysis (0.86 or greater in all cases). This study consisted of a high number of samples. Our data suggest that drawing a discard tube is still necessary for coagulation testing. Consideration should be given to revising the international guidelines related to the necessity of a discard tube for repeated evaluation of coagulation tests especially receiving long-term OAT.     

Patient safety and quality in laboratory and hemostasis testing: a renewed loop?

More than three decades ago, George Lundberg first introduced the concept of the brain-to-brain loop for laboratory diagnostics. According to this pioneering model, the first step in the loop involves the selection of laboratory tests in the brain of the physician caring for the patient, and the final step is the transmission of test results back to the ordering physician. There are several intermediary steps, some of which are preanalytical (e.g., identification of patient and blood samples, the process of blood collection, and specimen handling); some are analytical and relate to the actual performance of the test(s); whereas others are postanalytical and involve release of test results into the medical record and further steps such as the physician's reaction to laboratory information, their interpretation of these results, and subsequent appropriate clinical action. Hemostasis testing should also be viewed within such a paradigm, so that quality throughout the total testing process can be assured. For hemostasis testing, particular attention is required to ensure provision of appropriate test samples in the preanalytical phase. Nevertheless, the timeliness of testing and an appropriate interpretation of test results are also paramount. This article overviews the concept of quality testing within hemostasis as critical to ensuring patient safety and optimal clinical and therapeutic management.     

External quality assessment scheme for blood coagulation

The aim of setting an External Quality Assessment Scheme (EQAS) for Blood Coagulation is to achieve a harmonization among the participating laboratories on blood coagulation testing. In Indonesia EQAS for blood coagulation is organized by the Department of Clinical Pathology, Faculty of Medicine, University of Indonesia which cooperates with the Indonesian Society of Clinical Pathologists, Jakarta Chapter. Currently coagulation tests in Indonesia are only performed in a limited number of laboratories especially in the hospital. Therefore only 65 laboratories participated in the first trial of EQAS. The control material for EQAS was provided by Organon Teknika and parameters involved in the first trial were PT, INR, APTT, and fibrinogen. Currently there are 7 brands of reagents for coagulation tests available in the market, i.e.: Behring, Biomerieux, Biopool, Human, Nycomed, Organon, and Ortho. In the evaluation, the results of each participant were compared to the median of participants who used the same reagent. If the number of participants using a given reagent was less than 10, then the result of each participant was compared to the median of overall participants. The result of a given parameter was classified as within consensus if it fell into the range of median +/- 15%. In the overall evaluation, the percentage of participants which was classified as within consensus for PT, INR, APTT, and fibrinogen were 68%, 64%, 63%, and 67%, respectively, but the CV for PT, INR, APTT, and fibrinogen were 19.84%, 17.89%, 20.21%, and 23.96% respectively. In the evaluation of participating laboratories using Behring's reagent, the percentages of participants classified as within consensus for PT, INR, APTT, and fibrinogen were 72%, 82%, 54%, and 74%, respectively. For Organon's product users, the percentages of those parameters were 84.6%-90%, 48%-75%, 86%, and 67%, respectively. It is concluded that around two-thirds of overall participating laboratories achieved harmonization in the results of coagulation test, but the variation of all parameters is still wide.