Abstract
•It is good to know that sensitivity is an important measure in public health aspects instead of clinical fields. Likewise, PPV and NPV are among the measures which are more appropriate for advice about the validity of a diagnostic test for clinical purposes.•It is critically important to consider that accurate diagnosis is very important in appendicitis because of the urgent need for surgery in people who are truly positive, likewise, operating surgery for people who are not truly positive will have inconvenient effects.•Finally, for the prediction of an outcome, we need data from two different cohorts or at least from one cohort divided into two to first to develop a prediction model and subsequently validate it.•To make our methodological comments brief, it is crucial to know that to determine the validity and predictive ability of ultrasound in predicting acute appendicitis among children, methodological and statistical issues should be correctly taken into account.