Immunodiagnosis of meningeal leukemia using the alkaline phosphatase procedure.

To optimalize the diagnosis of meningeal involvement in ALL we adapted the alkaline-phosphatase-anti-alkaline-phosphatase procedure (APAAP) to be used for cerebrospinal fluid (CSF) examination. The study was performed on 19 patients (9 children with leukemia) with CSF hypercellularity. 490 determinations with a panel of 12 monoclonal antibodies were performed. This method was convenient, cell morphology was preserved so that combined morphological and immunological characterization of specific cells was possible in mixed cell populations. The combined study of immunological and morphological criteria produced more accurate results than those based on morphological criteria alone. The APAAP technique is useful for small numbers of cells. The preservation of antigenic reactivity in frozen CSF smears may be of use in reevaluation studies.