Recovery of birth weight z score within 2 years of diagnosis is positively associated with pulmonary status at 6 years of age in children with cystic fibrosis

Abstract

Objective: We recently reported that 60% of children newly diagnosed with cystic fibrosis who had pancreatic insufficiency responded to treatment initiation and achieved catch-up weight gain to a level comparable with their birth weight z score within 2 years of diagnosis ("responders"), whereas the remaining 40% failed to do so ("nonresponders"). The present study examined the impact of this early weight recovery on subsequent growth pattern and pulmonary status at 6 years of age.

Patients and methods: Sixty-three children with cystic fibrosis who had pancreatic insufficiency but no meconium ileus, and were enrolled in the Wisconsin Cystic Fibrosis Neonatal Screening Project, were studied. Responders were defined by a recovery of weight z score comparable with that at birth within 2 years of diagnosis. From ages 2 to 6, growth was measured by both height and BMI. Pulmonary status was evaluated by symptoms, spirometry, quantitative chest radiography, and respiratory microbiology.

Results: The majority (71%) of the responders maintained their early weight recovery through 6 years of age, whereas only 32% of the nonresponders achieved substantial growth improvement from 2 to 6 years of age. Proportionately fewer responders reported cough symptoms (10% daytime cough; 22% nighttime cough) compared with nonresponders (41% daytime cough; 45% nighttime cough) at age 6. The percentage of predicted forced expiratory volume in 1 second at age 6 was 11% higher in responders (99.5% +/- 13.9%) compared with nonresponders (88.3% +/- 18.5%). Responders had significantly better Brasfield (20.1 +/- 1.4) and Wisconsin chest radiograph (8.3 +/- 3.3) scores compared with nonresponders (Brasfield: 18.9 +/- 1.8; Wisconsin: 12.3 +/- 8.3). Respiratory microbiology results were not significantly different. Multiple regression analyses indicated that the positive association between responder and percent predicted forced expiratory volume in 1 second at 6 years of age remained statistically significant after controlling for infections with Pseudomonas aeruginosa and Staphylococcus aureus and chest radiograph scores. Growth patterns from 2 to 6 years of age were not associated with pulmonary measures at age 6.

Conclusions: Patients with cystic fibrosis with pancreatic insufficiency who achieved early growth recovery within 2 years of diagnosis had fewer cough symptoms, higher lung function, and better chest radiograph scores at 6 years of age.

Figure 1

Schematic of growth pattern definition from diagnosis to age six years. Recovery of birth weight z-score is represented by responders, who achieved catch-up weight gain to a level comparable to their birth weight Z-score within 2 years of CF diagnosis. Non-responders are those who did not gain sufficient weight to achieve a weight z-score comparable to their birth weight z-score within 2 years of diagnosis.

Figure 2

Pulmonary function as indicated by percent predicted FEV₁ according to responder status and growth category.

Figure 3

Chest radiographic scores according to responder status and growth category. The first panel shows mean Brasfield score (32) within each group. A better Brasfield result is indicated by a higher score. The second panel shows mean scores using the Wisconsin scoring method (30, 31). Lower values from the Wisconsin method indicate fewer chest x-ray abnormalities. *One extreme value was excluded in the calculation of mean and SD.