This blog post was written by María Lazo-Porras, Andrea Ruiz, Cesar Ugarte-Gil, Aldo Lucchetti, Germán Málaga, María Kathia Cárdenas, María Amalia Pesantes
Leprosy, like many rare diseases, can often go undetected or mismanaged. Consequently, there is a need for more accurate diagnostic tests to ascertain cases of leprosy, particularly in resource-limited settings, to improve case management.
Leprosy is a chronic infectious disease produced by Mycobacterium leprae, primarily affecting the skin and peripheral nerves. Delayed diagnosis can lead to sensory loss of the affected area, deformities, mutilation, disability or more serious complications. Leprosy is defined as a neglected tropical disease by the World Health Organization, however there were more than 200,000 new cases globally in 2013. (1) In Latin America, the prevalence of leprosy has been greatly reduced. In Perú specifically, the prevalence is 1% or less, with cases often concentrated in cities, disproportionately affecting vulnerable groups. (2)
The diagnosis of leprosy is usually based on clinical signs and symptoms, which are easily observed with appropriate training. (3) However, diagnosis can be complicated by the presence of other diseases such as diabetes, which is increasingly common in Perú and other Latin American countries. Symptoms of leprosy can be easily confused with diabetes complications or mistaken for other skin conditions such as fungal infections, psoriasis, systemic lupus, leishmaniasis and neurofibromatosis. Therefore, leprosy diagnosis often relies on the observation of a chronic skin lesion, which is more difficult to treat. Educational programmes directed at clinicians, other health workers and the general public, alongside the development of improved diagnostic tests are urgently needed to improve early detection and diagnosis of cases.
Skin tests for leprosy diagnosis are available, however they are not accurate enough (have a low specificity). (4) Approaches to improving leprosy diagnosis would benefit from the use of novel and standardized laboratory techniques to measure pre-symptomatic infection and develop a point-of-care test to detect new cases. Several immunological diagnostic tests have been developed but, until recently, they were not very sensitive. Molecular techniques as Polymerase Chain Reaction (PCR) have also been tested, providing a sensitivity of 100%. However, their high cost and the complexity of implementing such a test in rural areas is a big limitation. (5) Efforts to reduce the cost and improve the accuracy of such tests would greatly facilitate their widespread use.
- Singh PK. Leprosy needs renewed efforts, greater push. World Health Organization. 2015. Available from: http://www.searo.who.int/mediacentre/features/2015/world-leprosy-day/en/. [Accessed 20th December 2015].
- Soto-Cabezas M. Epidemiología de la Lepra en el Perú: retos y perspectivas para la eliminación. Boletín del Instituto Nacional de Salud. 2015. Available from: http://www.dge.gob.pe/portal/docs/vigilancia/boletines/2013/03.pdf. [Accessed 13th December 2015].
- World Health Organitazion. Diagnosis of leprosy. World Health Organization [Internet]. 2015. Available from: http://www.who.int/lep/diagnosis/en/. [Accessed 14th December 2015]
- Huebner RE, Schein MF, Bass JB Jr. The tuberculin skin test. Clin Infect Dis. 1993; 17: 968–975
- Reibel F, Cambau E, Aubry A. Update on the epidemiology, diagnosis, and treatment of leprosy. Med Mal Infect. 2015 Sep; 45(9):383-93.