Symptoms and reflux in infants: Infant Gastroesophageal Reflux Questionnaire Revised (I-GERQ-R)--utility for symptom tracking and diagnosis.

Answering a need for a thoroughly validated infant gastroesophageal reflux questionnaire, the Infant Gastroesophageal Reflux Questionnaire Revised (I-GERQ-R) was designed, refined, and validated using state-of-the-art psychometric methods. Diagnostic and evaluative (tracking) validity was identified. However, perplexing results of some clinical trials using the I-GERQ-R for diagnosis prompted analysis of possible reasons, including ambiguities in defining symptomatic gastroesophageal reflux disease (GERD) and aspects of the validation process. Symptomatic GERD is defined by "troublesomeness" of symptoms and attribution of their causation to reflux--two crucial issues. Methods of quantifying symptom-reflux associations are described and their limitations identified. The location of "symptomatic esophageal GERD" in the continuum of erosive GERD, histologic GERD, and nonerosive reflux disease is indicated, with the last including "suberosive," "premicroscopic," and "functional heartburn" subcategories. Another category is defined solely by surrogate measures of propensity to GERD (e.g., acid exposure thresholds defined on esophageal pH monitoring). During diagnostic validation of the Infant Gastroesophageal Reflux Questionnaire (I-GERQ) instruments, asymptomatic normals were contrasted with symptomatic GERD infants (who also tested positive with esophageal histology and esophageal pH monitoring). However, the diagnostic validation did not attempt to distinguish symptomatic GERD infants from symptomatic infants without GERD. The I-GERQ-R is thus adequately sensitive to be used diagnostically to screen infants for symptom burden, but should probably be supplemented by other, perhaps invasive, testing to assure appropriate specificity. The I-GERQ-R's validation for evaluative properties, however, supports its use for tracking symptoms within clinical trials.