Does nerve examination improve diagnostic efficacy of the WHO classification of leprosy?

Background: In the year 1998 WHO proposed that the clinical criteria of counting skin lesions alone should decide whether a patient receives Multibacillary (MB) or Paucibacillary (PB) MDT. There is a concern that a significant number of patients may be incorrectly treated under these guidelines.
Aims: This study aims to determine whether the sensitivity and the specificity of the latest WHO criteria, can be enhanced by the addition of nerve examination in the place of slit skin smears.
Methods: 150 patients of untreated leprosy reporting at a TLM Hospital in Delhi from January to December 2006 were registered for the study. After physical examination, the number of skin lesions and nerves involved were counted and slit skin smears performed. Two groups were created, those with > 5 skin lesions, and those with 5 or less skin lesions. The diagnostic efficacy of the current WHO classification was calculated with and without the addition of nerve examination.
Results: The sensitivity and the specificity of the current WHO operational classification are 76.6%, and 73.7% respectively, using slit skin smear as a standard. When the number of nerves was added to the diagnosis, the sensitivity increased to 94.4%, for more than 5 lesions and to 90.9%, for five or less than five lesions.
Conclusions: Nerve examination can significantly improve the sensitivity of the WHO criterion in determination of MB versus PB leprosy.

Keywords
Diagnosis of leprosy, Nerve enlargement, World Health Organization criteria