The external quality assessment scheme: Five years experience as a participating laboratory.

BACKGROUND AND AIM: Quality assurance in blood banking includes active participation in the external quality program. Such a program offers valuable benefits to patient care, their safety, and an overall quality of laboratory practices. In the year 2002, we participated in the External Quality Assessment Scheme (EQAS) under the World Health Organization (WHO), Bureau of Laboratory Quality Standards, Thailand. MATERIALS AND METHODS: In the current study we evaluated our EQAS test result of the past five years, from 2003 to 2007. Test results of all blood samples such as ABO grouping, D typing, antibody screening, antibody identification, and transfusion transmitted infection (TTI) testing were analyzed and documented. RESULTS: Discordant results in one or more instances were observed with antibody identification, weak D testing, and tests for anti-HIV1/2 and HBsAg. Twice we failed to detect the 'anti-Mia' antibody in the issued sample and that could be attributed to the absence of the corresponding antigen in the used cell panel. HBsAg was missed due to its critically low titer in the serum and the comparatively low sensitivity of our Enzyme-Linked Immunosorbent Assay (ELISA) test kit. CONCLUSION: All these failures in the last five years have helped us to significantly improve our transfusion service in terms of performance evaluation, patient care and safety issues, and the overall quality of laboratory practices. We therefore recommend all laboratories and hospitals to participate in the EQAS program, which will definitely help them to improve from what they learn.

A comparison of conventional tube test and gel technique in evaluation of direct antiglobulin test.

In vivo coating of red cells by antibody and/or complement is detected using various sensitive techniques, however most hospitals even today rely on the conventional tube technique (CTT). We compared the performance of the CTT and recently introduced gel test (GT) in the evaluation of direct antiglobulin test (DAT). The CTT and GT were first compared using in-house prepared control cells. The polyspecific DATs were performed simultaneously by CTT and GT on 170 consecutive blood samples. Positive samples were further tested for monospecific IgG and C3d by both techniques. GT demonstrated stronger agglutination scores (60 vs. 43) compared to CTT using control cells. The sensitivity and specificity of the GT was 98.4 and 95.2%, respectively as compared to CTT for polyspecific DAT. Discordance between the two test systems was seen in 6/170 patients. Of these, 5 were missed by CTT while GT failed to detect in vivo coating in only 1 case. The agreement between two methods of DAT was 96.4% (kappa = 0.926) using polyspecific AHG and 95.7% (kappa = 0.379) with monospecific anti-IgG. We conclude that GT is a better alternative to CTT for detecting red cell bound antibodies in various clinical conditions.

Application of flow cytometry in detection of red-cell-bound IgG in Coombs-negative AIHA.

Coombs negative autoimmune hemolytic anemia (AIHA) is characterized by laboratory evidence of in vivo hemolysis along with a negative direct antiglobulin test (DAT) performed by conventional tube technique (CTT) in clinically suspected AIHA patients. The sensitive gel test (GT) and flow cytometry (FC) can effectively diagnose such patients where CTT does not detect low level of red cell autoantibodies. We investigated the use of FC in the serological evaluation of CTT DAT negative AIHA and its comparison with GT DAT. Of the 50 patients with suspected AIHA, CTT DAT was negative in 5 patients (Coombs negative AIHA). GT DAT could detect red cell autoantibodies in 4 of these 5 patients. Monospecific GT DAT showed IgG and/or C3d as the responsible autoantibody. FC was considered as reactive when MFI was >3.6 (mean of 20 healthy negative volunteers +2SD). FC was reactive in all five Coombs negative AIHA patients. The mean MFI in five known CTT DAT positive samples taken for comparison was significantly higher compared to 5 DAT negative AIHA (18.3 +/- 7.78 vs. 7.88 +/- 1.35, p < 0.05). There was poor correlation between strength of GT DAT and MFI by FC. We conclude that FC is more sensitive test than the CTT and helps in the serological diagnosis of Coombs negative AIHA. However, in resource poor settings, GT DAT can be a good alternative to FC.