The relationship between detection delay and impairment in leprosy control: a comparison of patient cohorts from Bangladesh and Ethiopia

[[[ Introduction: ]]] It is acknowledged that longer delays between first symptoms and diagnosis result in increased impairment in newly detected leprosy patients. However, it is unclear whether detection delay in relation to impairment can be used as a general or absolute performance indicator of leprosy control programmes. It is unknown whether similar delays always result in similar proportions of impairment. Therefore, the present study examined the quantitative relationship between delay and impairment in two different patient populations. [[[ Methods: ]]] Patients from two study cohorts (BANDS and AMFES) who reported voluntarily were included in the analysis. Data on detection delay, WHO impairment status, type of leprosy, age and sex were analysed using descriptive statistics and multivariate logistic regression analysis to identify significant risk factors for impairment and to quantify the relationship between detection delay and impairment status at intake. [[[ Results: ]]] Detection delay was an independent risk factor for impairment at presentation in multivariate analysis. The AMFES cohort reported more impairment at detection than BANDS. In multivariate analysis, this difference was significant among PB patients (51% in AMFES versus 15% in BANDS), but not in MB patients (56% in AMFES versus 45% in BANDS). In fact, for every delay category PB patients from AMFES had much higher proportions of impairment than PB BANDS patients. Impairment rates in MB patients from AMFES were higher in every delay category, but the differences between the two cohorts were much smaller compared to PB patients. [[[ Conclusions: ]]] Our analysis confirms earlier findings that with longer delays, the risk of impairment at presentation increases. With the same reported delay, however, the proportion impaired can vary considerably between different patient populations, in particular for PB leprosy. Delay can therefore not simply be used as a general or absolute performance indicator for programme evaluation. Achieving short delays remains important in general, but understanding and addressing the underlying mechanisms of delay specific to a patient population adds substantially to the effectiveness of leprosy control.