Quantitative reverse transcription-PCR comparison of tumor cell enrichment methods.

platelet plots are not always seen in cryoglobulinemia, although other interferences are usually detected with high efficiency. For comparison, whereas the Technicon H*3 appeared to provide a more immediate visual indication of sample cryoglobulins, large platelet count overestimates were still obtained in most cases. Examination of graphic plots is not used in all laboratories, and its efficiency may be limited when workload is high. Without it, operators depend on the presence of other hematologic abnormalities, instrument flags, or clinical information. Because patients with cryoglobulinemia, both at clinical presentation and during treatment, almost always show abnormal erythrocyte or leukocyte results, morphologic review is likely. When spurious platelet counts are suggested by graphic or morphologic review, a systematic approach to subsequent investigation can be initiated. Initially, warming samples (.30 min at 37 °C) before instrument analysis generally resolves cryoglobulin interference and enables platelet counting by standard optical or impedance methods. When interference persists after rewarming, other causes should be considered. When doubt remains regarding the true platelet count, the conventional alternative is manual hemacytometry, but its imprecision is unacceptably high when the platelet count is ,20 3 10/L. The CD4000 CD61 immunoplatelet count, however, has high precision in thrombocytopenia (4 ) and, moreover, is not influenced by the presence of cellular or plasma interferences (Fig. 1D). Despite the cost of the test (approximately US $16 in Germany), immunoplatelet counting should be considered in situations such as platelet transfusions and therapeutic interventions with bleeding risk. Few reports have described platelet count interference by cryoglobulins, although awareness of the potential analytical problems is high. Because the presence of thrombocytopenia was masked in two of the four cases described here, we believe that cryoglobulin interference is an important concern for the clinical laboratory.