Classification of Hansen's Disease (leprosy) is based on clinical evaluation, skin smears from several sites and ideally at least an initial biopsy. The Ridley-Jopling classification of the disease is the one usually used in the United States. The following terms denote disease ranging from early localized (I) to generalized (LL):
While this classification gives one considerable information about the disease in an immunologic sense, the use of the World Health Organization's limited duration multidrug therapy has led to the widespread adoption of the WHO classification. This includes only the following:
In the U.S., generally only the terms paucibacillary and multibacillary are used when discussing drug regimens. Paucibacillary patients are those who are skin smear negative and no evidence of more advanced disease on biopsy. Multibacillary patients are those who are skin smear positive and/or have a biopsy indicating more advanced disease. Generally PB disease is equivalent to I, TT and BT disease in the Ridley-Jopling classification, and MB is equivalent to BB, BL and LL disease.