Throat Swab in the Chronic Tonsillitis: How Reliable and Valid is it?

M Kurien, A Stanis, A Job, Brahmadathan, K Thomas
Correspondence: Dr Mary Kurien, kurien_mary@hotmail.com

ABSTRACT
Introduction The diagnostic test of swabbing the surface of the tonsil as a culture specimen for the determination of the organism responsible for the tonsil infection is still in practice, despite controversy. To date there has been no reports of establishing the reliability and validity of this common diagnostic test by appropriate statistical test of Likelihood ratios taking into consideration the specificity and sensitivity.
Aims To assess the reliability and validity of throat swab in the diagnosis of bacterial microflora in chronic tonsillitis.
Patients and Methods A prospective study of 40 patients clinically diagnosed to have chronic tonsillitis undergoing tonsillectomy was undertaken. The reliability of the throat surface swab was then assessed and validated with the reference (gold) standard of tonsil core culture.
Results The likelihood ratio of this diagnostic test being positive (LR +ve) was 0.84 to similar and 1.3 to general organism pathogen.
Conclusion Routine culture of the throat by surface swab in the accurate diagnosis of bacterial flora in chronic tonsillitis is neither reliable nor valid. The clinical implications of this investigation which is still very popular is discussed.

Keywords: Throat swab, tonsil core culture, gold standard, reliability, validity, sensitivity, specificity, likelihood ratio
Singapore Med J 2000; 41(7): 324-326