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

Objectives: To develop a valid and reliable quantitative measure of leprosy Type 1 reactions. Methods: A 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. Results: The 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. Conclusions: We 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. Author Summary: Leprosy is caused by a bacterium and is curable with a combination of antibiotics known as multi-drug therapy which patients take for six or 12 months. However, a significant proportion of leprosy patients experience inflammation in their skin and/or nerves which may occur even after successful completion of multi-drug therapy. These episodes of inflammation are called leprosy Type 1 reactions. Type 1 reactions are an important complication of leprosy because they may result in nerve damage which leads to disability and deformity. Type 1 reactions require treatment with immunosuppressive agents such as corticosteroids. The severity of Type 1 reactions varies with time, treatment and between individuals. We have developed a clinical severity scale to measure the severity of Type 1 reactions. The scale has three sections. The first measures the involvement of the skin using the number of affected skin lesions, the degree of inflammation of those lesions and the presence of swelling of the hands, feet or face. The second section is a measurement of the sensory function of the nerves supplying the eyes, hands and feet by assessing a patient's ability to feel graded nylon fibres. The third section uses a standard measure of muscle power to assess motor function of the nerves of the face, hands and feet. The clinical severity scale we have developed will facilitate the study of Type 1 reactions and enable direct comparison between different studies. This will improve the management of this disabling complication of leprosy.