Evaluation of Polymerase Chain Reaction(PCR) and Adenosine Deaminase Activity for the Diagnosis of Tuberculous Effusions in Children

Om Prakash Mishra ^1*, rahul kumar ¹, ziledar ali ², rajniti prasad ¹ and gopal nath ³

¹ Departments of Pediatrics, Institute of Medical Sciences, Banaras Hindu University, Varanasi-22, India
² Departments of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
³ Departments of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India

^* To whom correspondence should be addressed. E-mail: opmpedia{at}yahoo.co.uk.

Accepted 18 May 2006

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 transdutative 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 non-tuberculous group. The mean fluid ADA and ALC values were significantly raised in tuberculous in comparison to non-tuberculous effusions (P < 0.001). The sensitivity and specificity of PCR, ADA ( > 38IU/l), and ALC ( > 275/mm3) were 74%, 88%, 81%, 75% and 90%, 83%, respectively in diagnosing tuberculous effusions. The sensitivity of PCR, ADA and ALC were 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 taken positive, then specificity markedly increased (92-96%) but sensitivity of the tests decreased.

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

Keywords: ADA(adenosine deaminase), PCR( polymerase chain reaction), PPD(purified protein derivative), Z-N(Ziehl-Neelsen)

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