Routine ventilation scans in children with cystic fibrosis: diagnostic usefulness and prognostic value

Krypton ventilation scans (VS) provide an index of peripheral lung function , and may be particularly useful in children unable to perform pulmonary fu nction testing. This communication reports on three linked studies which in vestigated whether a routine VS in young children with cystic fibrosis (CF) is diagnostically or prognostically useful. Study 1: In a preliminary stud y in 1991, VS were compared with clinical examination and chest radiography (CXR) in 50 CF children (29 females, 21 males) aged 0.4-5.2 years (median 2.2 years). The chest was divided into six zones, and abnormalities scored from 0 (normal) to 2 (very abnormal). Clinical examination was unhelpful in predicting abnormalities on imaging. In five children (10%) with a normal CXR, VS was abnormal, and in a further eight children (16%). CXR markedly u nderestimated VS changes. Study 2: In order to determine the long-term prog nostic significance of VS abnormalities, we followed up 27 (19 females, 8 m ales) of the children from study 1, who had had their first VS at presentat ion at median age 1.6 years (range 0.4-5.2), scoring the same six zones fro m 0 to 2. Followup was for a mean of 11.6 years (range 7.8-14.8). Spirometr y at age 7 years showed a mean forced expiratory volume in I s (FEV1) of 96 % (range 46%-145%) and a mean forced vital capacity (FVC) of 96% (range 46% -145%). A poor VS score at presentation was correlated with percent predict ed FEV1 at age 7 (r=0.4, P=0.042, 16% of variance explained). Those with a normal VS at presentation had a mean FEV1 at presentation of 99% (range 80% -129%). Whereas four patients had an abnormal VS, a normal CXR and a low FE V1 at age 7 years, no patient had a normal VS, an abnormal CXR and a low FE V1 at age 7 years. Study 3: Fifty children (29 females, 21 males) aged 0.5- 6.0 years (median 3.8) were prospectively studied in 1998, to determine whe ther the findings in study I were stable over time, and to assess whether V S altered clinical management. Symptoms and clinical examination did not pr edict abnormalities on imaging. Thirty (60%) children had a normal VS while only five (10%) had a normal CXR. There was a significant correlation betw een the total scores of CXR and VS (P=0.007, 14% of variance explained). Fu rther, VS detected additional abnormalities in seven patients (14%). Sixty- five percent of patients with an abnormal VS had modifications of treatment , including bronchoscopy, compared with 23% of those with a normal VS. We c onclude that VS is a simple, safe and non-invasive technique giving additio nal information to that provided by clinical examination and chest radiogra phy in a number of children with CF and can be used to modify clinical mana gement. VS at presentation gives prognostic information, which may be of us e in early intervention studies. Whether using VS to guide treatment improv es long-term prognosis requires a larger prospective trial.