Nasopharyngeal aspiration for diagnosis of pulmonary tuberculosis

Stephen Owens ¹, Isam E Abdel-Rahman ¹, Stephen Balyejusa ², Phillipa Musoke ², Richard Cooke ³, Christopher M Parry ⁴ and J B S Coulter ^1*

¹ Liverpool School of Tropical Medicine, United Kingdom
² Makerere University, Kampala, Uganda
³ Medical Microbiology, University Hospital Aintree, United Kingdom
⁴ Medical Microbiology, University of Liverpool, United Kingdom

^* To whom correspondence should be addressed. E-mail: coulters{at}fulwood11.wanadoo.co.uk.

Accepted 12 December 2006

Abstract

Background: Confirmation of pulmonary tuberculosis in young children is difficult as they seldom expectorate sputum.

Aim: To compare sputa obtained by nasopharyngeal aspiration and by sputum induction for staining and culture of Mycobacterium tuberculosis.

Patients and methods: Patients from Mulago Hospital, Kampala with symptoms suggestive of pulmonary tuberculosis, were considered for inclusion in the study. Those with a positive tuberculin test and/or a chest radiograph compatible with tuberculosis were recruited. Infection with human immunodeficiency virus was confirmed by duplicate enzyme-labelled immunosorbent assay or in children <15 months, by polymerase chain reaction. Direct polymerase chain reaction was undertaken on 82 nasopharyngeal aspirates.

Results: Of 438 patients referred, 94 were recruited over a period of 5 months. Median (range) age was 48 (4-144) months. Of 63 patients tested 69.8% were infected with human immunodeficiency virus. Paired and uncontaminated culture results were available for 88 patients and smear results for 94 patients. Nasopharyngeal aspirates were smear-positive in 8.5% and culture-positive in 23.9%. Induced sputa were smear- positive in 9.6% and culture positive in 21.6%. Overall 10.6% were smear-positive, 25.5% were culture-positive and 26.6% had smear and/or culture confirmed tuberculosis. Direct polymerase chain reaction on nasopharyngeal aspirates had a sensitivity of 62% and specificity of 98% for confirmation of culture-positive tuberculosis.

Conclusions: Nasopharyngeal aspiration is a useful, safe and low-technology method for confirmation of pulmonary tuberculosis and like sputum induction can be undertaken in outpatient clinics.

Keywords: diagnosis, nasopharyngeal aspirates, sputum induction, tuberculosis

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