Periodic acid-Schiff stain in childhood acute lymphoblastic leukemia: lack of independent prognostic value.

The authors reviewed 250 consecutive children with ALL to determine if the periodic acid-Schiff (PAS) score was a useful, independent predictor of time to failure. PAS stains were scored from 0 to 400 and divided into low- and high-score groups using a variance-ratio test (F test) to optimize any effect of PAS on prognosis. Although the effect of PAS score considered alone approached significance for time to failure, the PAS score lost all significance when the patients were divided into standard-risk and high-risk groups on the basis of peripheral white count, central nervous system involvement, mediastinal mass, or E-rosette positivity at diagnosis. A Cox regression analysis was performed on a subgroup of 198 patients for whom cytogenetic studies were also available. The PAS score again approached the level of significance when considered alone but was of no significance after the effects of peripheral white count, pseudodiploidy, mediastinal mass, and E-rosette positivity were removed. The authors conclude that the PAS stain has no independent prognostic significance in childhood ALL.