Development and validation of the Molluscum Contagiosum Diagnostic Tool for Parents: diagnostic accuracy study in primary care.

BACKGROUND: Molluscum contagiosum (MC) is diagnosed by its distinct appearance. Parental diagnosis of MC may reduce anxiety and lead to reductions in healthcare consultations, and may be particularly useful in large-scale epidemiological studies. However, there are currently no published, validated tools allowing parental diagnosis of MC. AIM: To develop and validate a tool for parental diagnosis of MC. DESIGN AND SETTING: The Molluscum Contagiosum Diagnostic Tool for Parents (MCDTP) was developed and its diagnostic accuracy was compared with GP diagnosis in 12 GP surgeries in South Wales. METHOD: Following development, which involved three phases with dermatologists, nurses, GPs, and parents, parents completed the MCDTP (index test) in the practice waiting room, and rated their confidence in their diagnosis. A GP then examined their child for MC (reference test). Test characteristics were calculated for all responders and for those who expressed being confident or very confident in their diagnosis. RESULTS: A total of 203 parents completed the MCDTP. The MCDTP showed a sensitivity of 91.5% (95% confidence intervals (CI) = 81.3 to 97.2) and a specificity of 88.2% (95% CI = 81.8 to 93.0) in all parents and a sensitivity of 95.8% (95% CI = 85.7 to 99.5) and a specificity of 90.9% (95% CI = 83.9 to 95.6) in parents who were confident or very confident in their diagnosis. The positive predictive value was 76.1% (95% CI = 64.5 to 85.4) and negative predictive value was 96.2% (95% CI = 91.4 to 98.8) for all parents. CONCLUSION: The MCDTP performed well compared with GP diagnosis and is suitable for clinical use by parents and in population-based studies.