Major criteria

Minor criteria

Father or mother with asthma diagnosed by a medical doctor.

Eczema diagnosed by medical doctor.

Allergic rhinitis diagnosed by medical doctor

Wheezing episodes not related to colds

Eosinophilia in peripheral blood (>4%)

A modified API (mAPI) was used in a randomized clinical study that involved 285 participants, included allergic sensitization to one or more allergens as another major criterion, and allergic sensitizing to milk, eggs, or peanuts as a minor criterion, which replaced the medical diagnosis of allergic rhinitis from the original API. Other predictive indexes were developed to predict persistent wheezing.

In 2003 Kurukulaaratchy et al. developed a predictive index using the information gathered from 1456 participants of the Wight Island study. This study found that having a family with a background history of asthma, positive cutaneous allergy tests at 4 years of life, and lower respiratory tract infections at 2 years of life were related to an increase in the probability of presenting with asthma symptoms at 10 years of life. Sensitivity, specificity, and positive and negative predictive ratio were 10%, 98%, 83%, and 64%, respectively, and the positive and negative likelihood ratios were 7.9 and 0.91, respectively. However, external validation studies are still needed to confirm this information.

In 2009, Caudri et al., using the information gathered from 3963 children from the PIAMA study, developed a predictive index named risk score PIAMA, based on eight clinical parameters easily obtained in daily clinical practice (masculine sex, birth after term, educational level of the parents, parent use of inhaled medications, frequency of wheezing episodes, wheezing not related to cold-like episodes, number of infections of the respiratory airway, and diagnosis of atopic dermatitis). When this index was used for the cohort in the PIAMA study, the participants with a score of 30 or greater had a 40% probability of developing asthma at 7 to 8 years of life.

Predictive asthma indexes, especially API, have been questioned. The indexes have been used in clinical practice without having a validation procedure in different populations (external validation). They have not been probed to predict long-term wheezing, the most severe wheezing episodes in children. They have also been found relatively complex with no real benefit over using more simple prediction rules based only on the frequency of wheezing episodes. Nevertheless, recently the API index and PIAMA risk score have been validated in independent populations (Colombia, 130 children; England, 1954 children). The API is a broad-use predictive index easily obtainable in any health center. API has been used with several purposes, such as a criterion of high-risk asthma development in randomized clinical trials, as well as a guide in clinical practice for the treatment of preschoolers with recurrent wheezing. API has been included in the most important guidelines for asthma management in the world, such as the Global Initiative for Asthma (GINA) and the proposal made by the National Institutes of Health (NIH) of the United States of America.

A recent study designed to validate the modified PIAMA risk index (term-born was replaced by prematurity as a criterion, and the infections in the respiratory system were eliminated) in a multiethnic cohort in the Netherlands (R Generation) showed that it has an acceptable discrimination rate and a good calibration in comparison with the original PIAMA cohort. It was also noted that it was independent of different ages and the ethnic origin of preschoolers. In comparison to the original PIAMA, the modified index had a discrete better negative value prediction, a poorer positive value prediction, and a similar positive and negative likelihood ratio (97% versus 95%, 74% versus 76%, 2.4 versus 2.5, and 0.5 versus 0.5, respectively). The Clinical Asthma Prediction Score (CAPS) followed 711 Danish preschoolers who sought primary attention for cough, wheezing, or respiratory distress. These children were followed up until they reached 6 years of age, when the diagnosis of asthma was based on the clinical combination, use of antiasthma medication, and pulmonary function (methacholine hyperreactivity, or bronchial reversibility by spirometry). This study showed a negative and positive predictive value of 0.74 to 0.78, respectively, but external validation studies are needed.

It is important to highlight that the best parameter to determine the use of a diagnostic test is the probability or coefficient variation (positive likelihood ratio), which for API is 7.3. Thus, for a population at low, moderate, or high risk of suffering from asthma during school age (for example, 10%, 20%, and 40%), if a child is evaluated for recurrent wheezing, API application increases the probability of asthma prediction by 4.3 to 2 fold, respectively. In other words, the asthma pre-test frequency will change from 10% to 42%, from 20% to 62%, and from 40% to 80%, respectively. Additionally, the most useful feature of the API is its ability to estimate the probability that preschoolers with recurrent wheezing continue to have asthma symptoms during school age. Therefore, the use of API and other indexes of asthma prediction are valid within the clinical context to reduce morbidity in preschoolers with recurrent wheezing who are at a greater risk of developing asthma. All these measures are intended to avoid the unnecessary prescription of follow-up therapies in children who tend to have only transient conditions instead of asthma.

There are three important reasons to diagnose asthma in children under 5 years old who have recurrent wheezing along with a positive predictor index. First, about 80% of patients with asthma present symptoms during the first 5 years of life. Second, the greater reduction in pulmonary function happens before reaching 5 years of life. Third, even in developed countries, the population of children with the poorest asthma control are children less than 5 years old. Therefore, it is probable that parents will adhere better to determined prolonged follow-up treatment if they know that the cause of recurrent wheezing their child presents is a chronic disease called asthma, instead of a disease with a milder-sounding name as sometimes mentioned (“allergy” or “bronchial hyperreactivity,” “recurrent bronchitis,” “asthma-like bronchitis,” “obstructive bronchitis,” “pre-asthma,” or “principles of asthma”). We know that adherence, measured by electronic dosimeters, to inhaled steroids when treating chronic asthma in children is only about 50%. Poor adherence to preventive treatment is one of the most important risk factors for uncontrolled asthma and hospitalization.