Leprosy other diagnostic studies
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
Although there are no laboratory studies to help in the diagnosis of leprosy, other studies such as biopsy of skin lesions and skin smear tests have an important contribution for the diagnosis of leprosy in patients, whose diagnosis is suspected from the clinical presentation.
Other Diagnostic Studies
Smear test
May be obtained from any skin lesion, from the nasal mucosa and/or the ear lobe. This test has a sensitivity of 50% and a specificity of 100%. After collection of the [Laboratory specimen|specimen]], in order to visualize the bacteria, the Ziehl-Neelsen stain should be used. According to the Global Initiative from the WHO, in countries where leprosy is endemic, the diagnosis should be made based on the clinical signs and the results of the smear test, despite the availability of more sophisticated tests, such as serology tests.[1][2][3][4]
Skin Biopsy
A biopsy of the skin lesion should be performed and stained according to the Fite-Faraco technique (a especially designed protocol for staining the leprosy bacilli). According to the pole of leprosy in that patient, typical findings include:[1]
- Tuberculoid pole:
- Bacilli are commonly not observed.
- Granulomas commonly found, containing:
- Epithelioid cells.
- Lymphocytic infiltrate.
- Langerhans cells.
- Common nerve involvement.
- Lepromatous pole:
- Inflammatory infiltrate.
- Virchow cells loaded with bacilli.
- Loss of adnexal structures.
Lepromin Test
Although not a diagnostic test, the lepromin skin test is used to classify and determine the prognosis of the condition. For this test it is used the inactivated form of Mycobacterium leprae, extracted from lepromas, as follows:[1]
- Intradermal injection of lepromin (the antigen) on the forearm.
- The result will then be interpreted at 2 moments:
- 1. Early reaction (Fernandez reaction):
- Good sensitivity.
- Cross reactivity with other mycobacteria.
- May be read at 24 or 48h.
- 2. Later reaction (Mitsuda reaction):
- Read at the 21st day.
- Positive result is expressed by a nodule measuring more than 5 mm.
- Indicative of resistance to the mycobacterium leprae.
Serology
The serology test using the PGL-1 antibody titer (Phenolic Glycolipid 1) is a useful diagnostic tool, particularly for multibacillary cases. However, it is not a good test for paucibacillary cases.[1][5]
Polymerase Chain Reaction
References
- ↑ 1.0 1.1 1.2 1.3 Eichelmann, K.; González González, S.E.; Salas-Alanis, J.C.; Ocampo-Candiani, J. (2013). "Leprosy. An Update: Definition, Pathogenesis, Classification, Diagnosis, and Treatment". Actas Dermo-Sifiliográficas (English Edition). 104 (7): 554–563. doi:10.1016/j.adengl.2012.03.028. ISSN 1578-2190.
- ↑ Hatta M, van Beers SM, Madjid B, Djumadi A, de Wit MY, Klatser PR (1995). "Distribution and persistence of Mycobacterium leprae nasal carriage among a population in which leprosy is endemic in Indonesia". Trans R Soc Trop Med Hyg. 89 (4): 381–5. PMID 7570870.
- ↑ Aggarwal A, Pandey A (2010). "Inverse sampling to study disease burden of leprosy". Indian J Med Res. 132: 438–41. PMID 20966523.
- ↑ Ramaprasad P, Fernando A, Madhale S, Rao JR, Edward VK, Samson PD; et al. (1997). "Transmission and protection in leprosy: indications of the role of mucosal immunity". Lepr Rev. 68 (4): 301–15. PMID 9503866.
- ↑ Silva EA, Iyer A, Ura S, Lauris JR, Naafs B, Das PK; et al. (2007). "Utility of measuring serum levels of anti-PGL-I antibody, neopterin and C-reactive protein in monitoring leprosy patients during multi-drug treatment and reactions". Trop Med Int Health. 12 (12): 1450–8. doi:10.1111/j.1365-3156.2007.01951.x. PMID 18076551.