The value of sputum induction in pediatric
asthma lies in its potential to directly and noninvasively assess airway
inflammation in children, because bronchoscopy and biopsy carry some risk. The Childhood
Asthma Management Program (CAMP) study was designed to evaluate the long-term effects of
budesonide and
nedocromil compared with placebo in children with mild to moderate
asthma across 8 centers.
OBJECTIVE: At the Denver CAMP site, we sought to evaluate the safety of sputum induction, to determine differences in airway
inflammation between treatment groups by using induced sputum analysis, and to examine correlations between other
biomarkers and sputum eosinophils.
METHODS: RESULTS: Ninety of 117 children provided an adequate sputum sample for analysis. In 9 subjects (3
nedocromil and 6 placebo), sputum induction resulted in
bronchospasm. These subjects had greater disease severity, as measured by a lower median prebronchodilator FEV 1 percentage predicted (85.0% vs 96.0%; P =.024) and FEV 1 /FVC ratio (70.0% vs 79.0%; P =.0008); greater
bronchodilator reversibility (16.5% vs 6.8%; P =.004); higher serum
IgE (1390.0 vs 495.0 ng/mL; P =.017) and circulating eosinophil count (757.0 vs 282.0/mm 3; P =.04); greater use of
prednisone (1.9 vs 0.9 courses per 100 person-years; P =.05); and greater supplemental inhaled
steroid doses (85.3 vs 0 mg; P =.016). At treatment discontinuation,
budesonide-treated patients had a lower median (1st, 3rd quartile) sputum percentage eosinophil (SPEos) (0.2% [0%, 1.2%] vs 0.8% [0.2%, 4.6%]; P =.03) compared with those treated with placebo; no significant difference was noted between
nedocromil- and placebo-treated patients. Higher SPEos at the time of treatment discontinuation was associated with
asthma worsening that required rescue
prednisone (n = 23) during the washout period compared with patients who remained stable (3.6% [0.4%, 6.4%] vs 0.6% [0.2%, 3.2%] SPEos; P =.023). Finally, greater SPEos was associated with atopy, higher
bronchodilator reversibility, lower FEV 1 /FVC ratio, higher exhaled
nitric oxide levels, circulating eosinophils, sputum and
serum eosinophil cationic protein, more
prednisone courses during the treatment period, and greater
asthma severity.
CONCLUSIONS: Sputum induction is a relatively noninvasive and safe procedure that can provide information on eosinophilic
inflammation and treatment response and is also associated with several measures of
asthma control. However, this procedure still remains a research tool in
asthma because of its requirements for technical expertise.