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Overdiagnosis of malaria in patients with severe febrile illness in Tanzania: a prospective study

BMJ 2004; 329 doi: https://doi.org/10.1136/bmj.38251.658229.55 (Published 18 November 2004) Cite this as: BMJ 2004;329:1212
  1. Hugh Reyburn (hugh.reyburn{at}lshtm.ac.uk), clinical senior lecturer1,
  2. Redepmta Mbatia, clinical epidemiologist2,
  3. Chris Drakeley, parasitologist1,
  4. Ilona Carneiro, statistician1,
  5. Emmanuel Mwakasungula, clinician3,
  6. Ombeni Mwerinde, data manager2,
  7. Kapalala Saganda, hospital superintendent4,
  8. John Shao, executive director2,
  9. Andrew Kitua, director general3,
  10. Raimos Olomi, professor2,
  11. Brian M Greenwood, professor1,
  12. Christopher J M Whitty, clinical senior lecturer1
  1. 1 London School of Hygiene and Tropical Medicine, London WCIE 7HT
  2. 2 Kilimanjaro Christian Medical Centre, Moshi, Tanzania,
  3. 3 National Institute of Medical Research, Dar es Salaam, Tanzania
  4. 4 Mawenzi Hospital, Moshi, Kilimanjaro, Tanzania
  1. Correspondence to: H Reyburn
  • Accepted 8 September 2004

Abstract

Objective To study the diagnosis and outcomes in people admitted to hospital with a diagnosis of severe malaria in areas with differing intensities of malaria transmission.

Design Prospective observational study of children and adults over the course a year.

Setting 10 hospitals in north east Tanzania.

Participants 17 313 patients were admitted to hospital; of these 4474 (2851 children aged under 5 years) fulfilled criteria for severe disease.

Main outcome measure Details of the treatment given and outcome. Altitudes of residence (a proxy for transmission intensity) measured with a global positioning system.

Results Blood film microscopy showed that 2062 (46.1%) of people treated for malaria had Plasmodium falciparum (slide positive). The proportion of slide positive cases fell with increasing age and increasing altitude of residence. Among 1086 patients aged ≥ 5 years who lived above 600 metres, only 338 (31.1%) were slide positive, while in children < 5 years living in areas of intense transmission (< 600 metres) most (958/1392, 68.8%) were slide positive. Among 2375 people who were slide negative, 1571 (66.1%) were not treated with antibiotics and of those, 120 (7.6%) died. The case fatality in slide negative patients was higher (292/2412, 12.1%) than for slide positive patients (142/2062, 6.9%) (P < 0.001). Respiratory distress and altered consciousness were the strongest predictors of mortality in slide positive and slide negative patients and in adults as well as children.

Conclusions In Tanzania, malaria is commonly overdiagnosed in people presenting with severe febrile illness, especially in those living in areas with low to moderate transmission and in adults. This is associated with a failure to treat alternative causes of severe infection. Diagnosis needs to be improved and syndromic treatment considered. Routine hospital data may overestimate mortality from malaria by over twofold.

Footnotes

  • We thank the patients and their families who participated in this study. We also thank the clinical and laboratory staff who assisted in data collection: Mark Swai, Werner Shimana, Ole Nguyaine, Cleopa Mbwambo, Justina Mushi, Francis Assenga, Joseph Minja, Alan Minja, William Silayo, Richard Mcharo, Raymond Urassa, Richard Collins, Hilda Mbakilwa, Sia Nelson, Nsia Muro, Elizabeth Msoka, Theresia Mtui, Sarah Mushi, Michael Irira, Esther Lyatu, Alutu Masokoto, Frank Magogo, Nico Funga, Lincoln Male, William Chambo, and Zacharia Zafaelli.

  • Contributors HR, RM, CD, and CJMW were involved in design, implementation, analysis, and writing up. IC and OM were responsible for data analysis, writing up of the results, and making critical revisions to the manuscript. KS and EM were each responsible for clinical data collection in the largest sites and made critical revisions on the paper. JS, AK, BMG, and RO were actively involved in the design of the study and planning the analysis and made critical revisions to the manuscript. Eleanor Riley, Daniel Chandramohan, Jon Cox, W M M Nkya, Martha Lemnge, Thor Theander, Joanna Schellenberg, and Jane Bruce also contributed to design, analysis, and reviewing the manuscript. HR is guarantor.

  • Funding Medical Research Council, UK (grant No 9901439). CJMW is supported by the Gates Malaria Partnership.

  • Competing interests None declared.

  • Ethical approval The ethical committees of the National Institute of Medical Research, Tanzania, and the London School of Hygiene and Tropical Medicine approved the study.

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