Diagnosing human African trypanosomiasis in Angola using a card agglutination test: observational study of active and passive case finding strategies

doi:10.1136/bmj.38859.531354.7C

BMJ 2006;332:1479 (24 June), doi:10.1136/bmj.38859.531354.7C (published 15 June 2006)

Research

Diagnosing human African trypanosomiasis in Angola using a card agglutination test: observational study of active and passive case finding strategies

Walter O Inojosa, medical officer¹, Inacio Augusto, laboratory technician¹, Zeno Bisoffi, doctor in chief², Teofile Josenado, director³, Paulo M Abel, medical coordinator¹, August Stich, head of clinical tropical medicine⁴, Christopher J M Whitty, professor of international health⁵

¹ CUAMM-Angola and Angotrip Project, Caritas, Luanda, Angola, ² Centro per le Malattie Tropicali, Ospedale S Cuore, Negrar, Verona, Italy, ³ Instituto de Combate e Controlo das Tripanossomoiases, Ministério da Saúde, Luanda, ⁴ Department of Tropical Medicine and Epidemic Control, Medical Mission Institute, Würzburg, Germany, ⁵ Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1B 3DP

Correspondence to: W O Inojosa, Universidade Católica de Moçambique Ponta Gêa Rua Marquês de Soveral, 960 CP 821, Beira, Mozambique inojosawalter{at}hotmail.com

Abstract

Objective To assess the operational feasibility of detectinghuman African trypanosomiasis by active and passive case findingusing the card agglutination test with serial dilution of serumto guide treatment.

Setting Trypanosomiasis control programme in the Negage focus,northern Angola, during a period of civil war.

Design Observational study.

Participants 359 patients presenting themselves to health centreswith symptoms (passive case finding) and 14 446 people activelyscreened in villages.

Main outcome measures Whole blood and serological tests at differentdilutions using the card agglutination test, and detection ofparasites by microscopy.

Results Active case finding identified 251 people with a positivecard agglutination test result, 10 of whom had confirmed parasites.In those presenting for investigation 34 of 51 with a positivecard agglutination test result at the dilution of 1:8 or moreused to guide treatment had parasites in blood, lymph node fluid,or cerebrospinal fluid, compared with 10 of 76 in those detectedby active case finding: positive predictive values of 67% forpassive case detection and 13% for active case detection. Onlyat a cut-off dilution more than 1:32 was the positive predictivevalue in active case detection reasonable (46%) and at thisdilution 40% of microscopically proved cases were missed.

Conclusions The card agglutination test is useful for initialscreening in active detection of cases with human African trypanosomiasisbut, given the toxicity of the drugs, serology using the cardagglutination test should be not used alone to guide treatmentafter active case finding. A second confirmatory test is needed.

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