Lactate dehydrogenase levels in aqueous humor and serum in retinoblastoma

The lactate dehydrogenase (LDH) levels were measured in the aqueous humor and serum of 16 patients (20 eyes) with retinoblastoma. The enzyme activity in the aqueous humor and serum did not show any correlation with each other. Age of presentation, age of enucleation, sex and disease duration had no correlation with the enzyme level either in the serum or aqueous humor. The stages of retinoblastoma were classified in Stages I to V: eyes with Stages I to III were included in Group 1, and those with Stages IV and V were in Group 2. The differences in LDH levels in the aqueous humor and in the aqueous to serum LDH ratio were highly significant (P less than 0.001) by Wilcoxon's nonparametric test between Groups 1 and 2. A considerable rise in the aqueous humor LDH level was observed without any alterations in the serum levels in Group 2 as compared to Group 1; hence the aqueous/serum ratio was increased in the former group. The LDH level in the aqueous humor and the aqueous/serum ratio can be a diagnostic tool in retinoblastoma of Stages IV and V. Though the lower aqueous levels of LDH do not rule out the presence of the disease, the higher levels are definitely helpful for diagnosis of retinoblastoma.