Serial sputum galactomannan as an adjunctive biomarker for the diagnosis of Aspergillus-related airway involvement in patients with cystic fibrosis

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Sputum galactomannan index (GMI) has been proposed as an adjunctive biomarker for diagnosing Aspergillus -related airway involvement. This study evaluated sputum GMI as a screening biomarker for Aspergillus colonization and chronic pulmonary aspergillosis (CPA) in people with cystic fibrosis (pwCF). In this two-year multicenter prospective study, pwCF referred to the Iranian CF Foundation who provided at least two sputum samples within 6 months were enrolled. The optimal sputum GMI cut-off was determined by receiver operating characteristic (ROC) analysis. Participants were classified as negative, transient colonization (TC), persistent colonization (PC), or CPA using an operational case definition for resource-constrained settings in the absence of Aspergillus -specific IgG testing. The diagnostic performance of sputum GMI was evaluated across these groups. Among 235 pwCF, 545 sputum specimens were analyzed for fungal culture and GMI. Of 304 Aspergillus isolates, A. flavus (30.9%) was the predominant species. Overall, 13.6%, 6.8%, 41.3%, and 38.3% of participants were classified as CPA, PC, TC, and negative, respectively. Median sputum GMI was significantly lower in the negative group (0.58) than in the CPA (0.68) and PC (0.87) groups. GMI was also significantly higher in the combined clinical group (CPA and PC) than in the non-clinical group (TC and negative) ( P < 0.001). ROC analysis yielded an AUC of 0.67 (95% CI, 0.584–0.768), with an optimal GMI cut-off of ≥ 0.67 (sensitivity, 62%; specificity, 62%). Sputum GMI may serve as a useful adjunctive screening biomarker for clinically significant Aspergillus airway involvement in pwCF but should complement, rather than replace, conventional microbiological and clinical assessment.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.