Sweat chloride concentrations in children with Idiopathic Nephrotic Syndrome

Idiopathic Nephrotic Syndrome (INS) has been believed to cause a false positive elevation of sweat chloride concentrations, as measured by the sweat test.

Sweat tests were done for 11 children with acute onset INS at admission and again while they were in remission, with results being compared to normal historical controls.

The initial sweat chloride concentration for 10 patients was normal (mean16.7 ± 11.02 mmol/L) and 1 patient had inadequate collection. This latter patient and two others were excluded during follow-up because of diagnoses other than INS. Sweat test results for the eight INS patients during follow up remained unchanged when they were in remission (16.94 ± 7.88 mmol/L; P = 0.98; Wilcoxon Matched-Pairs Signed Rank Test). In comparing sweat chloride concentrations from INS patients to those from 20 historical control subjects, we found no significant differences (Mann-Whitney Test; initial vs. control P = 0.643; follow up vs. control P = 0.806).

INS does not cause a false positive sweat test. Further studies should be done to objectively assess the conditions that have been reported to affect sweat chloride concentrations.