A Review of Patients with False Positive Cystic Fibrosis Screening Tests in the Light of Current Literature

Abstract

Objective: Cystic Fibrosis (CF) is a chronic condition, may affect multiple systems and can show itself with repeated lung infections, meconium ileus, and pancreatic failure. It can even be seen in newborns. It is a genetic disorder that is passed down in autosomal recessive, which is thought to affect 1/2500-1/3000 people in Turkey. To start the treatment early, CF was added into newborns’ screening program using ImmunoReactive Trypsinogen (IRT) test. This retrospective study explores false positive results in children, who were referred to Social Pediatrics Clinic whose both CF tests are positive through evaluation with clinical examination and sweat tests. Methods: The Ethics Committee approved this retrospective study. These children were referred to a CF reference hospital for a definitive diagnosis. We studied patient files for all the relevant clinical data, socio-demographic factors, patient history, test results, and prognosis of those children who did not receive CF diagnosis although their both screening tests were positive. We statistically explored what factors might have caused these false positives. Results: Sixteen cases were included. Their mean age was 133.75 (±82.15) days. 57% of them were male. While there was a statistically significant relationship between gestational age, birth weight, and stay days in the Neonatal Intensive Care Unit, duration of antibiotics treatment, prolonged jaundice, death of siblings, and delayed meconium output, there was no statistically significant difference between the other groups. Conclusion: This study once again shows that there might be false positives in CF screening tests and identified factors that might have contributed to this. However, be mindful of false positives of these tests, we stress that the sweat test should definitely be applied to every patient whose tests were positive. Any patient with suspected clinical manifestations or test whose sweat test is not definitive or any patient with CF risk should certainly be re-evaluated as one should not forget that clinical symptoms may show up at a later age.