On what criteria does the WHO classify leprosy?

The World Health Organization (WHO) classifies leprosy primarily based on the number of skin lesions and the results of skin smear tests. This classification system is effective because leprosy manifests through specific skin lesions that indicate the presence of Mycobacterium leprae, the bacterium that causes the disease. The skin smear test helps confirm the diagnosis by identifying bacilli in the skin lesions, allowing for a more accurate classification of the disease.

While other factors such as neurological symptoms and physical deformities can provide additional context about the severity of the disease and its impact on the patient, they are not the basis for the formal classification by the WHO. Additionally, factors like geographic distribution and demographics may influence epidemiological data but do not directly relate to how leprosy is classified clinically. Thus, using skin lesions and smear test results is key to assessing and managing the condition effectively.