INTRODUCTION: Cystic Fibrosis (CF) is an autosomal recessive disorder and the 
incidence of this disease is undermined in Northern India. The distinguishable 
salty character of the sweat belonging to individuals suffering from CF makes 
sweat chloride estimation essential for diagnosis of CF disease.
AIM: The aim of this prospective study was to elucidate the relationship of 
sweat chloride levels with clinical features and pattern of CF.
MATERIALS AND METHODS: A total of 182 patients, with clinical features of CF 
were included in this study for quantitative measurement of sweat chloride. 
Sweat stimulation and collection involved pilocarpine iontophoresis based on the 
Gibson and Cooks methodology. The quantitative estimation of chloride was done 
by Schales and Schales method with some modifications. Cystic Fibrosis Trans 
Membrane Conductance Regulator (CFTR) mutation status was recorded in case of 
patients with borderline sweat chloride levels to correlate the results and for 
follow-up.
RESULTS: Out of 182 patients having clinical features consistent with CF, 
borderline and elevated sweat chloride levels were present in 9 (5%) and 41 
(22.5%) subjects respectively. Elevated sweat chloride levels were significantly 
associated with wheeze, Failure To Thrive (FTT), history of CF in Siblings, 
product of Consanguineous Marriage (CM), digital clubbing and steatorrhoea on 
univariate analysis. On multivariate analysis only wheeze, FTT and steatorrhoea 
were found to be significantly associated with elevated sweat chloride levels 
(p<0.05). Among the nine borderline cases six cases were positive for at least 
two CFTR mutations and rest of the three cases were not having any mutation in 
CFTR gene.
CONCLUSION: The diagnosis is often delayed and the disease is advanced in most 
patients at the time of diagnosis. Sweat testing is a gold standard for 
diagnosis of CF patients as genetic mutation profile being heterozygous and 
unlikely to become diagnostic test.