Original Article| Volume 22, ISSUE 1, P73-78, January 2023

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Different management approaches and outcome for infants with an inconclusive diagnosis following newborn screening for cystic fibrosis (CRMS/CFSPID) and Pseudomonas aeruginosa isolation


      • Pseudomonas aeruginosa (Pa) isolation occurs frequently in asymptomatic CRMS/CFSPID.
      • Spontaneous clearance occurs frequently in CRMS/CFSPID Pa-positive infants.
      • Management can vary for CRMS/CFSPID Pa-positive infants.
      • Overmedication can occur in CRMS/CFSPID Pa-positive infants.



      Evidence is currently lacking to guide the management of cystic fibrosis (CF) transmembrane conductance regulator–related metabolic syndrome CF screen–positive inconclusive diagnosis (CRMS/CFSPID) with Pseudomonas aeruginosa (Pa)–positive respiratory culture. This study assessed the clinical data, management, and outcomes of an Italian cohort of CRMS/CFSPID infants with Pa isolated from their airways.


      Data of Pa-positive CRMS/CFSPID infants born between January 2011 and August 2018 and followed at five CF Italian centres were retrospectively extracted. Further data were collected until June 2021 to assess outcomes, prevalence of subjects treated with antimicrobials, and treatment type and duration.


      Forty-three asymptomatic CRMS/CFSPID patients (median age on 30 June 2021, 82 months; interquartile range [IQR], 63–98 months) with at least one positive airway culture for non-mucoid Pa (median age at first isolation, 18.7 months; IQR, 7–25 months) were enrolled. Of them, 24 (55.8%) underwent anti-Pa therapy. Pa clearance occurred in 22 (91.6%) of 24 patients versus spontaneous clearance in 16 of 19 (84.2%) untreated patients (chi-square, 0.5737; p = 0.44878). After a median follow-up of 6.2 years (IQR, 3.0–9.9), 7 (16.3%) were diagnosed with CF after a pathological sweat test (median age, 43 months; IQR, 28–77 months), 3 (7%) developed recurrent pancreatitis or isolated bronchiectasis consistent with CFTR-related disorder, and the CRMS/CFSPID classification remained in 33 (76.7%).


      Pa detection frequently occurs in asymptomatic infants with CRMS/CFSPID but tends to clear spontaneously. More studies are needed to determine if Pa isolation can predict evolution.



      CF (cystic fibrosis), CFSPID (CF screen–positive inconclusive diagnosis), CFTR (cystic fibrosis transmembrane conductance regulator), CFTR-RD (CFTR-related disorder), CRMS (CFTR-related metabolic syndrome), MLPA (multiplex ligation-dependent probe amplification), NBS (newborn bloodspot screening), Pa (Pseudomonas aeruginosa), FEV1 (forced expiratory volume in 1 s), ST (sweat test)
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