ObjectivesIn underdeveloped and developing countries where protein energy malnutrition (PEM) is common, it is sometimes difficult to exclude the diagnosis of cystic fibrosis (CF) in malnourished children because both primary PEM and CF share similar symptoms, signs, and laboratory findings, such as elevated sweat chloride value. This study was performed to investigate sweat test results and determine percentile values in children with primary PEM.MethodsA total of 90 children with PEM and 30 healthy children were included. PEM was classified according to criteria defined by Gomez, Waterlow, and McLaren. Sweat tests were performed using the Macroduct conductivity system.ResultsPatient age and gender did not affect the test results (P> 0.05). The mean sweat conductivity (equivalent NaCl mMol/L) of patients with PEM was higher than that of controls (P< 0.001) and increased with the degree of malnutrition (P< 0.001). Inverse correlations between sweat conductivity and weight for age, height for age, and weight for height were detected (P< 0.001). The highest value was found in children with wasting and stunting, followed by those with stunting (P< 0.05) and those with marasmic kwashiorkor (P< 0.01). Of all children with PEM, 6.7% had elevated sweat test results that normalized after nutritional management; of children with third degree PEM, the figure was 20%. Ninety-fifth percentile values of first, second, and third degree malnutrition were 47 mMol/L, 49 mMol/L, and 69 mMol/L, respectively.ConclusionElevated sweat test result is not an important problem, especially in first and second degree PEM, but borderline values can be detected in as many as 20% of cases of third degree malnutrition. Sweat conductivity may increase to 69 mMol/L in children with stunting, those with wasting and stunting, and in those with third degree PEM.