Objective: To establish a reliable cost-effective screening criterion for cystic fibrosis (CF) among underweight children suffering from frequent chest infections using the sweat chloride test (SCT).
Methods: In a cross-sectional study, 145 children with frequent chest infections were seen in the Pediatric Department at Prince Rashed Bin Al-Hassan Hospital, Irbid, Jordan, between January and December 2008. Their age ranged from 2-12 years (87 males and 58 females). We obtained 11 children with positive polymerase chain reaction (PCR) for CF from hospital laboratory records, and 134 had no confirmed CF. Nutritional anthropometric assessment of weight-for-age and height-for-age based on the Centers for Disease Control and Prevention/World Health Organization 2000 was performed only on the confirmed 11 cases of CF. We used receiver operating curve statistical analysis to find the best SCT cut-off value for screening CF.
Results: The identification of CF is highly sensitive and specific when using the SCT >57 mmol/L. The sensitivity was 100% (95% confidence interval; 71.3-100%), specificity was 90.3% (95% confidence interval; 84-94.7%), and the good reliability Kappa statistical agreement beyond chance was 58.5%.
Conclusion: A sweat chloride result of >57 mmol/L seems to strongly suggest the likelihood of CF, and should trigger further investigation in patients who have frequent respiratory symptoms and have failed to thrive.