title: Thrombocytopenia in malaria: can platelet counts differentiate malaria from other infections?
abstract: OBJECTIVE
  To determine the accuracy of thrombocytopenia as a diagnostic marker for malaria.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Department of Medicine, 1 Mountain Medical Battalion (Bagh, Azad Kashmir) from July to September 2013.
  
  
  METHODS
  Adult patients presenting with a short history of fever without any localizing symptoms or signs were included. Exclusion criteria included patients with fever of > 7 days duration, those in whom an underlying diagnosis could be easily confirmed on the basis of history and physical examination, those on antibiotics/ antimalarials or antiplatelet agents and patients with Dengue fever. Platelet counts in venous whole blood samples were analysed with Sysmex KX-21 Haematology analyzer. Thick and thin peripheral blood smears were then prepared and examined for malarial parasites. Diagnosis of malaria was established on the basis of smear findings.
  
  
  RESULTS
  There were 245 patients in total. Out of the 109 patients with thrombocytopenia, 61 had vivax malaria. Platelets count was normal in 136 patients, including 4 with vivax malaria. Falciparum malaria was not seen in any patient. All cases with malaria were uncomplicated. Various measures of accuracy thus calculated were sensitivity 93.85%, specificity 73.33%, positive predictive value 55.96%, negative predictive value 97.06%, positive likelihood ratio of 3.52, negative likelihood ratio of 0.08, diagnostic odds ratio 41.94 and diagnostic accuracy of 78.78%.
  
  
  CONCLUSIONS
  Thrombocytopenia has an excellent sensitivity and a very good specificity for vivax malaria. Normal platelet counts provide very strong evidence against malaria as the etiology of fever without a focus.
authors.affiliation: Department of Medicine, 1 Mountain Medical Battalion, Bagh, Azad Kashmir.
authors.forename: Abdul Rehman
authors.initials: AR
authors.lastname: Arshad
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D004909:Erythrocyte Indices; D005260:Female; D005334:Fever / Q000209:etiology*; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D015994:Incidence; D008288:Malaria / Q000097:blood* / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D016780:Malaria, Vivax / Q000097:blood / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010154:Pakistan / Q000453:epidemiology; D010966:Plasmodium vivax / Q000302:isolation & purification; D010976:Platelet Count; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013921:Thrombocytopenia / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology
chemical_list: D006454:Hemoglobins