Bone marrow acid phosphatase in prostate cancer: an assessment by immunoassay and biochemical methods.

Comparisons of the bone marrow and serum acid phosphatase values obtained by counterimmunoelectrophoresis and the Roy biochemical test were made in 72 patients with and in 13 patients without prostatic cancer. The counter-immunoelectrophoresis test, when positive at more than 1 international unit per liter, showed only 4.4% falsely positive results. The Roy biochemical test, which uses sodium thymolphthalein monophosphate as the substrate, had 65% falsely positive bone marrow acid phosphatase levels. Conflicting reports regarding the value of bone marrow acid phosphatase determinations in patients with prostatic cancer result from the use of non-specific substrates in biochemical methods for measurement and from the trauma incidental to bone marrow aspiration, which releases many non-prostatic acid phosphatase enzymes. The use of immunoassay such as counter-immunoelectrophoresis minimizes this source of error.