ELISA system for detection of immune responses to FVIII: a study of 246 samples and correlation with the Bethesda assay

Inhibitors of FVIII are usually IgG polyclonal antibodies that develop as alloimmune responses in patients with congenital haemophilia A or as autoimmune responses resulting in acquired haemophilia. Their recognition can be difficult, especially when the titre is low. Furthermore, results from a Bethesda assay often require several days as samples are referred to a specialty laboratory. The aim of this study is to assess the utility of an ELISA system for detecting immune responses to FVIII. A total of 246 plasma samples submitted from 176 individuals with immune responses to FVIII, as verified with the Bethesda assay, and samples from 50 control subjects were tested for the presence of FVIII-specific IgG using an ELISA-based assay. Paired sera from 18 of the patients were also tested by the ELISA. Of the 246 samples that were positive for a FVIII inhibitor by the Bethesda assay, 235 (95.5%) were also positive by ELISA. The regression coefficient, using Log BU was r = 0.82. The correlation data were strengthened when 27 inhibitor samples were diluted further. There was a strong correlation between ELISA results for the 18-paired serum and plasma samples (r = 0.99). There is a strong correlation between the ELISA and Bethesda methods in detecting immune responses to FVIII. The ELISA provides rapid screening that could be available well in advance of confirmation by the Bethesda assay.

Factor VIII inhibitors. Laboratory diagnosis of inhibitors

The diagnosis of inhibitors of blood coagulation is often the most challenging problem in the clinical laboratory. Immediate attention must be given to the following patient groups whose principal laboratory abnormality is the prolonged activated partial thromboplastin time (aPTT): the patient with (1) hemophilia who previously responded to an adequate dose of clotting factor product and now fails to show effective clinical response to the same replacement concentrate; (2) previously benign clinical history who now presents with soft tissue bleeding or emergent internal hemorrhaging; (3) sudden onset of generalized ecchymoses who was previously well; (4) postpartum state; (5) malignancy, lymphoma, rheumatoid arthritis, or other autoimmune disorders; and (6) drug reactions. Immediate attention must be given to the prolonged prothrombin time (PT), aPTT, and thrombin time (TT) in order to respond to urgent queries from a perplexed internist, hematologist, intensivist, or surgeon caring for a patient with unexpected bleeding. Sometimes the problem of a prolonged "clotting time" arises preoperatively, causing unanticipated delay in operative procedures. For this reason, the laboratory support, usually in the coagulation section of a clinical laboratory or reference laboratory, must be quick, unequivocal and precise. The most common finding is an isolated mild, moderate, or severe prolongation of the aPTT with a normal PT, TT, and platelet count. The aPTT mixing study (The Mix), usually modified for time and temperature, along with appropriate controls, is the seminal test. This is the basis for all further testing. It may be supported by direct factor assays, and, therefore, the laboratory must know the reagent responsiveness and sensitivity for each clotting factor. By definition, complete correction of the aPTT in a 1:1 mix of patient and reference plasma is a factor deficiency. In this article, incomplete or minimal correction of The Mix will be characterized with particular attention to the various inhibitor assays, in other words, Oxford, Bethesda, and Nijmegen assays and the enzyme-linked immunosorbent assay (ELISA). An investigative approach to final characterization of the intensity (quantification) of the inhibitor and the exclusion of a lupus anticoagulant (LA) will be discussed.

Cytomegalovirus-induced thrombocytopenia. An unusual case report

A 21-year-old man had severe thrombocytopenia resistant to corticosteroid therapy. Viral studies of cytomegalovirus were 1:1,024. Although the cytomegalovirus titer returned toward normal (1:16 titer) during a period of three months, thrombocytopenia persisted and continued to remain refractory to corticosteroid therapy. Initial bone marrow morphology, platelet size, and platelet survival and sequestration were not typical of idiopathic thrombocytopenic purpura, and it is doubtful that splenectomy would have been helpful. However, when restudied six months later, platelet size was greatly increased, platelet survival was severely shortened (half-time, 2 1/4 hours), and intense splenic trapping was evident. Splenectomy was performed and resulted in normalization of the platelet count. Cytomegalovirus-associated thrombocytopenic purpura is an unusual disease that may take an unpredictable clinical course. Careful study of the mechanism of thrombocytopenia appears worthwhile when early recovery does not occur.

Agranulocytosis caused by Chinese herbal medicines. Dangers of medications containing aminopyrine and phenylbutazone

Four non-Chinese patients, middle-aged or older, developed agranuloctyosis while taking Chinese herbal medicines for relief of arthritis and back pain. All four developed life-threatening infections with bacterial sepsis; one died. The herbal medicines were shown to contain substantial amounts of undeclared aminopyrine and phenylbutazone, drugs that are well-known causes of agranulocytosis. These Chinese herbal medicines are widely available over the counter throughout the United States.

Aspirin-induced prolongation of the ivy bleeding time. Its diagnostic usefulness

Ivy bleeding time values before and two hours after ingestion of 600 mg of aspirin (aspirin tolerance test) were studied in normal persons, in patients with a disorder of primary hemostasis and in patients with various coagulation factor deficiencies. Aspirin produced a significant prolongation of the bleeding time in patients with von Willebrand's disease, uremia, and primary platelet disease, and in two patients with Factor XI deficiency. Dextropropoxyphene hydrochloride caused no prolongation of the bleeding time in normal persons.