A multicenter validation of recombinant ß3 integrin-coupled beads to detect human platelet antigen-1 alloantibodies in 498 cases of fetomaternal alloimmune thrombocytopenia.

BACKGROUND: Fetomaternal alloimmune thrombocytopenia (FMAIT) is caused by human platelet (PLT) antigen (HPA) incompatibility. Beads coupled with recombinant ß3 integrins, displaying the biallelic HPA-1 epitopes (rHPA-1), have been shown to detect HPA-1a alloantibodies implicated in FMAIT. This report describes a multicenter validation of the beads using the results of well-characterized samples to define the optimum parameters for analysis of a large cohort of 498 clinical samples. STUDY DESIGN AND METHODS: Fifty-one blinded quality assurance (QA) samples were tested by six laboratories to standardize the rHPA-1 bead assay and to develop an algorithm for sample classification. Five laboratories retrieved samples from 498 independent FMAIT cases, previously tested by the monoclonal antibody-specific immobilization of PLT antigens (MAIPA) assay, from their local archives for testing with the rHPA-1 beads. The results were evaluated using a mathematical algorithm developed to classify the samples. RESULTS: The QA samples gave a mean concordance of 94% between the bead and MAIPA assays, while 97% concordance was observed with the FMAIT samples. Of the 15 discrepant samples, seven were positive by the beads but negative by MAIPA, while the contrary was observed for eight samples. Overall, the bead assay achieved 98% sensitivity for HPA-1a antibody detection in FMAIT and 98.7% specificity compared to the local MAIPA. CONCLUSION: The rHPA-1 bead assay is a rapid 3-hour assay for the sensitive detection of HPA-1 antibodies. Its ease of use would enable prompt detection of maternal HPA-1a antibodies in suspected FMAIT cases, which is important supportive evidence for treatment by transfusion with HPA-1b1b PLTs.

DRY TAP: A DIAGNOSTIC ALERT FOR UNDERLYING BONE MARROW PATHOLOGY.

BACKGROUND: Dry tap is an annoying experience in bone marrow (BM) findings, especially in cases where the diagnosis may hinge on BM findings. This study was conducted to determine, on, the basis of bone marrow (BM) trephine biopsy, the frequency of various underlying conditions causing a dry tap, among different age groups. METHODS: It was a descriptive study carried out at PAF hospital Mianwali, Pakistan from 1" Jan 2009 to 31 Dec 2012. Record of all BM aspirations and trephine biopsies performed during 4 years was retrieved from hospital's laboratory. Total number of BM aspirations and trephines were counted and the subject's ages and genders recorded. Frequencies and percentages of patients with dry tap, in paediatric group (<15 years of age), young to middle-aged group (15-59 years) and the elderly (> or = 60 years) were calculated. Diagnoses of patients with dry tap made on BM biopsy were noted for each group and their frequencies calculated. RESULTS: Of 548 BM aspirations, dry tap was encountered in 52 (9.5%) cases. Acute lymphoblastic leukaemia (ALL) was the commonest cause of dry tap in paediatric age, seen in 6 (60%) of 10 children. In young to middle-aged group, non Hodgkin lymphoma (NHL) was the commonest cause, found in 6 (30%) of 20 cases. NHL and metastatic tumours, seen in 8 (36.4%) and 6 (27.3%) of 22 patients respectively, were the most frequent causes of dry tap in the elderly. CONCLUSION: Dry tap, in most of the cases, is like a diagnostic alert for the presence of an underlying BM pathology, nature of which depends upon age group.