Some evidence has shown that platelet crossmatching is useful in multitransfused patients with hypoplastic bone marrows who are refractory to platelet therapy through alloimmunization. Several immunoglobulin binding assays other than enzyme-linked immunospecific assay (ELISA) have been studied previously. We performed 51 ELISA crossmatches on six patients receiving single donor platelets. One bone marrow transplant patient receiving 33 single donor HLA matched (related and unrelated) was also studied. Effectiveness of transfusion was closely monitored by patient evaluation and corrected platelet count increment (CCI) at 1-2 and 18-24 hours posttransfusion. We found the ELISA method very sensitive, specific, and predictive, 85, 96, and 95.6% respectively in the 51 crossmatches studied in six patients with either leukemia, solid tumors, or aplastic anemia. However, variation existed among individual recipients, with sensitivity ranging from 70-100%. The distribution of true positives and negatives and false positives and negatives in the 33 crossmatches performed in the bone marrow transplant patient differed significantly (chi 2 = 101.2; P less than 0.001) from single donor recipients. The specificity in the 51 crossmatches on the six patients was also significantly different from the 33 crossmatches performed in the bone marrow transplant (96 vs 74%). This suggests individual variation occurs as well as differences in diseases and bone marrow suppressive agents affecting platelet crossmatching.

Platelet crossmatching assays have been used to predict the outcome of platelet transfusions in alloimmunized patients by detecting antibodies against platelets. The transfusion failure of HLA-matched platelets predicted by platelet crossmatching may be related to HLA antibodies undetected by lymphocytotoxicity but detected by platelet immunoglobulin-binding assays or platelet-specific antibodies (both antibodies defined here as platelet-reactive antibodies). To differentiate platelet-reactive antibodies from lymphocytotoxic HLA antibodies, we used HLA characterized lymphocytes in parallel with platelets from individuals to form separate frozen panels. Sera from 10 allosensitized patients were studied in the lymphocyte panel by lymphocytotoxicity and in the platelet panel by enzyme-linked immunoassay (ELISA). By comparing pattern and percent wells reacting in each panel, lymphocytotoxic HLA antibodies and antibodies reactive with platelets in ELISA were detected separately. In all 10 allosensitized patients, platelet-associated antibodies were present and 7 had additional lymphocytotoxic HLA antibodies. Using this double parallel panel technique, we found platelet-reactive antibodies important in platelet alloimmunization, unrecognized by lymphocytotoxicity. These data indicate platelet-crossmatching be solely used in the selection of platelets for allosensitized patients.

Fibronectin, a major component of the extracellular matrix and basement membranes throughout the body, is thought to maintain the integrity of both the reticulo-endothelial system and microvasculature. In this study, plasma fibronectin levels were assayed by nephelometry in nine pre-eclamptic gravid women, nine normotensive gravid women and ten non-gravid women. The mean plasma fibronectin level (+/-S.E.M.) in pre-eclamptic gravidas (1687 +/- 101 micrograms/ml) is significantly higher than that of either normotensive gravidae (1129 +/- 99 micrograms/ml) or non-gravid women (897 +/- 60 micrograms/ml). Although the mechanism for elevated levels of plasma fibronectin in patients with pre-eclampsia is not clear, it may serve as an early biochemical marker for this disorder.

Several companies have developed commercial kits to measure plasma fibronectin rapidly and inexpensively with readily available laboratory equipment. In two of these kits (Cooper Biomedical and Boehringer-Mannheim) an immunoturbidimetric method is used. In a third kit (Biomedical Technologies, Inc.) an enzyme immunoassay method is used. To evaluate these commercial kits for fibronectin assay, we selected nephelometry as a comparison method for ranking the kits with regard to precision and accuracy. We also compared antibody and fibronectin cross reactivity. The antibodies from various manufacturers appear similar, but the fibronectin standards from different sources showed significant variation. Rate nephelometry and the Boehringer-Mannheim kit had the best within-run precision (CVs of 0.38% and 5.5% respectively). Between-run precision for nephelometry was excellent (CV = 1.9%) and somewhat high for the Boehringer-Mannheim kit (CV = 15.4%). This study demonstrates a need for further standardization of antigen (fibronectin) and antibody in commercial kits and the development of suitable stable quality-control material.