Levels of serum ribonuclease as an indicator of renal insufficiency in patients with leukemia

Serum ribonuclease (RNase) levels were measured in 29 patients with leukemia at various times during their illness and compared with 54 normal controls and 29 nonleukemic patients on chronic hemodialysis. 83% of the leukemic patients examined before therapy and with normal rates of glomerular filtration (as defined by creatinine clearance greater than 60 ml/min) had RNase levels that fell within the mean ± 2 sigma for the normal controls. 61% of the leukemic patients, studied at various times during the course of their illness, who had a creatinine clearance of >60 ml/min had RNase levels in the normal range. 93% of the leukemic patients studied with a creatinine clearance of <60 ml/min had RNase levels above the range established for the normal controls. Patients without leukemia, but on hemodialysis for chronic renal failure of varied etiologies, had markedly elevated serum RNase levels. A strong correlation between RNase levels and renal insufficiency is therefore demonstrated, illustrating that changes in RNase levels over periods of time depend on the rate of glomerular filtration and are not related to the extent of leukemia. The enzyme responsible for enhanced RNase activity as glomerular filtration rate declines is shown to be antigenically similar, if not identical, to the enzyme found in normal human plasma. In conclusion, serum RNase levels are an indication of the rate of glomerular filtration and are not a biomarker for the presence or extent of leukemia.