Research Article: Development and Validation of a Severity Scale for Leprosy Type 1 Reactions

Date Published: December 23, 2008

Publisher: Public Library of Science

Author(s): Stephen L. Walker, Peter G. Nicholls, C. Ruth Butlin, Jose Augusto C. Nery, Hemanto K. Roy, Emanuel Rangel, Anna M. Sales, Diana N. J. Lockwood, Edgar Carvalho

Abstract: ObjectivesTo develop a valid and reliable quantitative measure of leprosy Type 1 reactions.MethodsA scale was developed from previous scales which had not been validated. The face and content validity were assessed following consultation with recognised experts in the field. The construct validity was determined by applying the scale to patients in Bangladesh and Brazil who had been diagnosed with leprosy Type 1 reaction. An expert categorized each patient’s reaction as mild or moderate or severe. Another worker applied the scale. This was done independently. In a subsequent stage of the study the agreement between two observers was assessed.ResultsThe scale had good internal consistency demonstrated by a Cronbach’s alpha >0.8. Removal of three items from the original scale resulted in better discrimination between disease severity categories. Cut off points for Type 1 reaction severities were determined using Receiver Operating Characteristic curves. A mild Type 1 reaction is characterized using the final scale by a score of 4 or less. A moderate reaction is a score of between 4.5 and 8.5. A severe reaction is a score of 9 or more.ConclusionsWe have developed a valid and reliable tool for quantifying leprosy Type 1 reaction severity and believe this will be a useful tool in research of this condition, in observational and intervention studies, and in the comparison of clinical and laboratory parameters.

Partial Text: Leprosy is a chronic granulomatous disease caused by Mycobacterium leprae. More than 254 000 new cases were reported to the World Health Organization in 2007 [1].

In many branches of medicine a single test or diagnostic criterion is either not available or insufficient to adequately measure or describe a clinical syndrome. This has led to difficulties in measuring the severity and prognosis of conditions. The response by researchers has been to develop composite measurement scales.



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