Improving the diagnostic accuracy of cytologic cerebrospinal fluid examinations in acute lymphoblastic leukemia using high-power microscopy and terminal deoxynucleotidyl transferase determinations.

Abstract

In patients with acute lymphoblastic leukemia (ALL), cytologic examination of cerebrospinal fluid (CSF) is becoming increasingly important for clinical management. In order to enhance the diagnostic accuracy of CSF cytology results, the value of using terminal deoxynucleotidyl transferase (Tdt) and high-power (1,000x) light microscopy, together with conventional cytologic examination was assessed. In 33 CSF samples from ten multiply examined Tdt-positive ALL patients, original cytologic interpretations were compared to Tdt results. Cytology samples were reviewed by two pathologists (one with hematopathologic expertise). The cases in which cytologic interpretation did not correlate with Tdt result were first reviewed via 1,000x microscopy without knowledge of Tdt result, then re-reviewed with knowledge of Tdt result. Conventional cytology alone diagnosed 64% of cases accurately (Tdt representing the comparative standard). High-power microscopy increased the correlation to 82%. Use of high-power microscopy and knowledge of Tdt result together produced a total of 85% of cases with correlation of results. High-power microscopic examination therefore contributes significantly to the accurate diagnosis of ALL, and knowledge of the Tdt result at the time of cytologic examination produces an additional advantage in providing an objective measure for CSF involvement by leukemia. Using all three methods in conjunction is recommended in order to increase the overall accuracy of CSF examination for the detection of leukemic involvement in ALL patients.