RESUMO
INTRODUCTION: The literature lacks formally validated and reliable tools for the diagnosis of breakthrough cancer pain (BTcP). The Italian Questionnaire for BTcP diagnosis (IQ-BTP) is an 11-item questionnaire aimed at detecting potential-BTP and classifying it into three likelihood classes: high, intermediate, and low. METHODS: A multicenter, prospective, and observational study was designed to validate the IQ-BTP. In three consecutive visits with each cancer patient, the demographic and clinical details of the patient, the Brief Pain Inventory (BPI) scores, IQ-BTP outcomes, and clinicians' autonomous BTcP diagnosis (gold standard) and the agreement of this diagnosis with IQ-BTP outcomes were recorded. The assessed domains for IQ-BTP validation were: Validity, including content and face validity, construct validity (hypothesis testing, and cross-cultural validity\measurement invariance), and criterion validity; Reliability (internal consistency, reliability, and measurement error); Interpretability, and Responsiveness. RESULTS: Seven palliative and pain management facilities in Italy recruited 280 patients, yielding 753 evaluations. Using the IQ-BTP, the rate of potential-BTcP was 27.2%, of which its likely presence was high in 52.7% of patients, intermediate in 38.5, and low in 8.8%. The BPI item scores differed significantly between the two IQ-BTP classes (no-BTcP and potential-BTcP classes). The correlation of the latter class with BPI items was significant but low. The IQ-BTcP showed two principal components, accounting for 66.6% of the variance. Cronbach's α was 0.71. The agreement rate between the gold standard and IQ-BTP outcomes was 82%. Cohen's [Formula: see text] was 0.535. The IQ-BTP showed sensitivity and specificity of 69 and 86%, respectively. CONCLUSIONS: The IQ-BTP extensive formal validation showed satisfactory psychometric and validity properties. Its content, face, construct, and criterion validities and its reliability, interpretability, and responsiveness were shown. Its use enabled potential-BTcP to be identified and differentiated into three likelihood classes with direct therapeutic and epidemiological implications. The latter may be confirmed in future studies.