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Evaluation of polymerase chain reaction and adenosine deaminase assay for the diagnosis of tuberculous effusions in children
  1. O P Mishra1,
  2. R Kumar1,
  3. Z Ali2,
  4. R Prasad1,
  5. G Nath3
  1. 1Department of Pediatrics, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
  2. 2Department of Biochemistry, Institute of Medical Sciences
  3. 3Department of Microbiology, Institute of Medical Sciences
  1. Correspondence to:
    O P Mishra
    Department of Pediatrics, Institute of Medical Sciences, Banaras Hindu University, 12 G F, Kabir Colony, PO BHU, Varanasi 221005, India;opmpedia{at}yahoo.co.uk

Abstract

Aim: To evaluate and compare the utility of polymerase chain reaction (PCR) for the diagnosis of tuberculous effusions in children.

Methods: PCR, adenosine deaminase (ADA) activity and absolute lymphocyte count (ALC) were evaluated in the fluid of 31 tuberculous (20 pleural, 8 ascites and 3 pericardial) and 24 non-tuberculous (10 transudtative ascites, 8 empyema thoracis, 3 malignant pleural and 3 pyopericardium) effusions.

Results: Fluid PCR for Mycobacterium tuberculosis was positive in 74% of tuberculous effusions, whereas it was falsely positive in 13% of the non-tuberculous group. The mean fluid ADA and ALC values were significantly higher in tuberculous effusions than in non-tuberculous effusions (p<0.001). The sensitivity and specificity of PCR, ADA (⩾38 IU/l) and ALC (⩾275/mm3) were 74% and 88%, 81% and 75%, and 90% and 83%, respectively, in diagnosing tuberculous effusions. The sensitivity of PCR, ADA and ALC was 100%, 100% and 88%, respectively, for confirmed tuberculous effusions. When the two tests were combined (either/or positive), the sensitivity increased (90–100%) at the expense of specificity. When both the tests were positive, then the specificity markedly increased (92–96%), but sensitivity of the tests decreased.

Conclusion: Fluid PCR alone should not be relied on as a single test; rather, combined analysis with either ADA or ALC could be more useful in the diagnosis of tuberculous effusions in children.

  • ADA, adenosine deaminase
  • AFB, acid-fast bacillus
  • ALC, absolute lymphocyte count
  • BCG, Bacillus-Calmette Guerin
  • PCR, polymerase chain reaction

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Footnotes

  • Published Online First 31 May 2006

  • Competing interests: None declared.

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