Assessment of the performance of a capture immunoassay for the bone isoform of alkaline phosphatase in serum.

We report the analytical validation of an immunocapture assay for the bone isoform of alkaline phosphatase in serum. A between batch imprecision of less than 10% was found, being about 8% at the upper limit of the reference range, and with a detection limit of 0.8 IU/l at 37 degrees C. The crossreactivity of the method with the liver isoform was found to be in the range of 3-13% depending on the method employed. Unexpectedly the correlation of results with a non-immunological method for the quantitation of bone ALP showed significant differences between samples from children and patients with Paget's disease, with an apparent lower level of capture in the case of children. These data suggest that there may be differences in the epitope recognised by the antibody, which may be due to the presence of different forms of bone enzyme in these two populations. The significance of these observations is not clear at this stage.

Assessment of diagnostic utility of anti-CD34 in soft tissue tumors.

We have performed this study to define the usefulness of an anti-human progenitor cell antigen-1(anti-CD34) to distinguish some kinds of soft tissue tumors in formalin-fixed, paraffin-embedded tissues. Sixty three cases of vascular, fibrohistiocytic, neural and other tumors were immunostained for CD34 using the streptavidin-biotin immunoperoxidase method. All of the vascular tumors including hemangiomas, epithelioid hemangioendotheliomas, hemangiopericytomas, and lymphangiomas revealed strong CD34 positivity along the cytoplasmic membranes. Among the fibrohistiocytic lesions, all of five examples of dermatofibrosarcoma protuberans showed diffuse, strong, and linear staining along the cytoplasmic processes. In contrast, none of the benign fibrous histiocytomas and malignant fibrous histiocytomas expressed CD34. CD34-positive cells with delicate dendritic processes could be identified within the normal nerves, neuromas, neurofibromas, and Antoni B areas of neurilemomas. However, all of the malignant peripheral nerve sheath tumors were uniformly negative. In addition, an epithelioid sarcoma and four cases of leiomyosarcoma revealed focal, weak positivity with anti-CD34. In conclusion, this study demonstrated variable anti-CD34 staining pattern of certain fibrohistiocytic, muscle, and neural tumors and confirmed the potential usefulness of anti-CD34 in differentiating fibrous histiocytoma from dermatofibrosarcoma protuberans. It's also helpful to diagnose epithelioid hemangioendothelioma from other epithelioid-type tumors.