Validity and reproducibility testing of the Molar Incisor Hypomineralisation (MIH) Index.

Background: To address challenges presented to clinicians to diagnose and treat molar incisor hypomineralisation (MIH), a new assessment tool was created.

Aim: To explore the reproducibility and validity of a new instrument developed to assess MIH.

Methods: Inter-rater and test-retest reliabilities were examined using Cronbach's alpha. Thirty-five oral health professionals scored clinical photographs for the presence/absence of MIH and other enamel defects using the new index. Face, content, and construct validities were assessed. A panel of six experienced researchers assessed face validity. Construct validity was determined by examining hypothesised associations with clinical variables reported to change concurrently or as modifiers of the MIH outcome. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were also assessed.

Results: The index reflected the hypothesised associations regarding the presence, prevalence, and severity of MIH, demonstrating construct validity. Researchers indicated that codes and definitions were clear and suitable for international use. The index showed satisfactory scores of sensitivity/specificity and PPV/NPV. Examiners achieved "Substantial" to "Almost perfect" levels of agreement in clinical presentation and lesion extension.

Conclusions: The tested MIH index had reasonably solid properties providing confidence that it is a reliable and valid instrument for use in population-based and clinical screenings for diagnosis of MIH and other enamel defects.