Case detection delay in leprosy: Testing tool reliability and measurement consistency in Ethiopia, Mozambique, and Tanzania.

Background: Case detection delay (CDD) in leprosy is defined as the period between the onset of the first signs and symptoms and the time of diagnosis. A tool, consisting of a questionnaire and a detailed guide for researchers, which includes photos of typical skin signs and notes on establishing the timing of events, was developed to determine this period of delay in months in recently diagnosed leprosy patients. The aims of the study were to determine the reliability and consistency of this CDD assessment tool. Methods: This study was conducted in Ethiopia, Mozambique and Tanzania. Two types of consistency were considered: over time (test-retest reliability) and across different researchers (interrater reliability). A CDD questionnaire was administered to 167 leprosy patients who were diagnosed within 6 months prior to their inclusion. One month later, the same or another researcher re-administered the CDD questionnaire to the same patients. Both test-retest and interrater reliability were assessed using the intraclass correlation coefficient (ICC), where a value greater than or equal to 0.7 is considered acceptable. Results: In this study, 10 participants (6.0%) were under 15 years of age, and 56 (33.5%) were women. In the test-retest assessment, the mean CDD from the first and second interviews was 23.7 months (95% CI 14.4–34.8) and 24.0 months (95% CI 14.8–33.2), respectively. The ICC for test-retest reliability was 0.99 (95% CI 0.994–0.997). For the interrater reliability assessment, the first and second interviews revealed a mean CDD of 24.7 months (95% CI 18.2–31.1) and 24.6 months (95% CI 18.7–30.5), respectively, with an ICC of 0.90 (95% CI 0.85–0.94). A standard error of measurement of 0.46 months was found in the test-retest and 1.03 months in the interrater measurement. Most answers given by participants during the first and second interviews were matching (≥86%). Most non-matching answers were in the 0–2 month delay category (≥46%). Conclusion: The tool, including a questionnaire to determine the CDD of newly diagnosed leprosy patients, was validated in three African countries. The test-retest and interrater measurements demonstrated that the instrument is reliable and measures consistently. The tool can be used in routine leprosy programmes as well as in research settings. Author summary: Leprosy is an ancient infectious disease that still affects up to 200,000 new patients yearly worldwide, with an estimated three to four million people living with permanent disability. A delay in case detection is a major factor contributing to the development of disability. Case detection delay is defined as the interval between the onset of the disease's initial signs and symptoms and the time of diagnosis, comprising a 'patient delay' and a 'health-system delay'. The case detection delay tool was first designed in the cultural context of the East Hararghe Zone, Ethiopia, as part of the PEP4LEP project. Subsequently, it was standardised to enable cultural adaptation to other regions and countries. The aims of this study were to determine the reliability and consistency of this case detection delay (CDD) assessment tool. The studied tool was validated in Ethiopia, Mozambique and Tanzania. The test-retest and interrater measurements demonstrated that the instrument is reliable and measures consistently. The tool can be used in routine leprosy programmes, active case detection projects, and in studies such as the PEP4LEP project. The tool is available in English, Oromiffa (Afaan Oromo), Portuguese, and Swahili via the international leprosy knowledge centre Infolep: https://www.leprosy-information.org/resource/case-detection-delay-questionnaire [ABSTRACT FROM AUTHOR]