An index to predict asthma
Since 1980, the Tucson Children’s Respiratory Study has followed 1246 healthy newborns seen by pediatricians affiliated with a large HMO in Tucson, Arizona. Questionnaires about parental asthma history and prenatal smoking history were obtained at enrollment. Childhood wheezing and its frequency, as well as physician-diagnosed allergies or asthma, were assessed at ages 2 and 3. If the child had wheezed in the past year, then the child was considered to be an “early wheezer.” If the frequency was 3 or more on a 5-point scale, then the child was considered to be an “early frequent wheezer.” Questionnaires were re-administered at ages 6, 8, 11, and 13. Three episodes of wheezing within the past year or a physician diagnosis of asthma with symptoms in the past year was considered “active asthma.” Blood specimens for eosinophils were obtained at age 10.
Using these data, the researchers developed stringent and loose criteria (TABLE 1) and odds ratios (TABLES 2 and 3) for childhood factors most predictive of an asthma diagnosis at an older age. The findings of the study may help clinicians care for wheezing infants and toddlers.9
TABLE 1
A clinical index of asthma risk9*
| Major criteria | Minor criteria |
|---|---|
| Parental asthma (history of physician diagnosis of asthma in a parent) | Allergic rhinitis (physician diagnosis of allergic rhinitis as reported in questionnaires at ages 2 or 3 y) |
| Eczema (physician diagnosis of atopic dermatitis as reported in questionnaires at ages 2 or 3 y) | Wheezing apart from colds |
| Eosinophilia (≥4%) | |
| *Stringent index for predicting asthma: Child has early, frequent wheezing plus at least 1 of the 2 major criteria or 2 of the 3 minor criteria. Loose index for predicting asthma: Child has early wheezing plus at least 1 of the 2 major criteria or 2 of the 3 minor criteria. | |
TABLE 2
Likelihood of active asthma predicted by stringent index9
| Active asthma | OR (95% CI) | Sensitivity, % (95% CI) | Specificity, % (95% CI) | PPV, % (95% CI) | NPV, % (95% CI) |
|---|---|---|---|---|---|
| At 6 y | 9.8 (5.6-17.2) | 27.5 (24.6-30.4) | 96.3 (95.1-97.5) | 47.5 (44.3-50.7) | 91.6 (89.8-93.4) |
| At 8 y | 5.8 (2.9-11.2) | 16.3 (13.7-18.9) | 96.7 (95.4-98.0) | 43.6 (40.1-47.1) | 88.2 (85.9-90.5) |
| At 11 y | 4.3 (2.4-7.8) | 15 (12.6-17.4) | 96.1 (94.8-97.4) | 42.0 (38.7-45.3) | 85.6 (83.3-87.9) |
| At 13 y | 5.7 (2.8-11.6) | 14.8 (12.1-17.5) | 97.0 (95.7-98.3) | 51.5 (47.7-55.3) | 84.2 (81.4-87.0) |
| CI, confidence interval; NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value. | |||||
TABLE 3
Likelihood of active asthma predicted by loose index9
| Active asthma | OR (95% CI) | Sensitivity, % (95% CI) | Specificity, % (95% CI) | PPV, % (95% CI) | NPV, % (95% CI) |
|---|---|---|---|---|---|
| At 6 y | 5.5 (3.5-8.4) | 56.6 (53.3-59.9) | 80.8 (78.3-83.3) | 26.2 (23.4-29.0) | 93.9 (92.4-95.4) |
| At 8 y | 4.4 (2.8-6.8) | 50.5 (47.0-54.0) | 81.1 (78.3-83.9) | 29.4 (26.2-32.6) | 91.3 (89.3-93.3) |
| At 11 y | 2.6 (1.8-3.8) | 40.1 (36.8-43.4) | 79.6 (76.9-82.3) | 27.1 (24.1-30.1) | 87.5 (85.3-89.7) |
| At 13 y | 3.0 (1.9-4.6) | 39.3 (35.5-43.1) | 82.1 (79.1-85.1) | 31.7 (28.1-35.3) | 86.5 (83.9-89.1) |
| CI, confidence interval; NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value. | |||||
Recommendations
A European and United States expert panel guide to the diagnosis and treatment of asthma in childhood, PRACTALL, states that “asthma should be suspected in any infant with recurrent wheezing and cough episodes. Frequently, diagnosis is possible only through long-term follow-up, consideration of the extensive differential diagnoses, and by observing the child’s response to bronchodilator and/or anti-inflammatory treatment.”10
The National Asthma Education and Prevention Program’s Expert Panel Report 3 (EPR-3) notes that diagnostic evaluation for asthma in children 0 to 4 years of age should include history, symptoms, physical examination, and assessment of quality of life.1