Journal of Infection (1998) 36, 273-277 Detection of Mycobacterium tuberculosis in Serum Samples Using the Polymerase Chain Reaction M. van Staden *~, E. van der Ryst 2, E. M. Attwood ~, M. L. Hendricks ~, G. Joubert 3 and D. J. V. WeicW ~Department of lnternaI Medicine (G73), University of the Orange Free State, P.O. Box 339, Bloemfontein, 9300, South Africa, 2Department of Virology, University of the Orange Free State, Bloemfontein, South Africa, and 3Department of Biostatisties, University of the Orange Free State, BIoemfontein, South Africa Conventional methods for the diagnosis of Mycobacterium tuberculosis infections have serious limitations. To determine whether amplification of M. tuberculosis DNA in serum by the polymerase chain reaction (PCR) might be a useful additional diagnostic tool, we tested 329 clinical specimens using primers specific for the IS6110 insertion sequence of the M. tuberculosis complex. The samples consisted of 30 serum samples from healthy controls, 114 serum samples from patients with diagnoses other than tuberculosis (including immunosuppressive disorders), 59 samples from patients with a clinical picture suggestive of tuberculosis, and 78 serum samples from patients with proven M. tuberculosis infection. Both serum, and representative samples from anatomical regions suspected of being infected, were collected from a further 48 patients for comparison with serum PCR. Serum PCR identified 72/ 78 (92%; 95% confidence interval CI: 84%-97%) patients with proven tuberculosis, and 49/59 (83%; 95% CI: 71%-92%) patients with suspected tuberculosis. In the group of patients with other diagnoses, 30/114 (26%; 95% Ch 18%-34%) tested positive, while none of the specimens from the healthy control group were positive (95% Ch 0%-12%). Serum PCR results also compared favourably with other clinical specimens obtained from the same patient. Serum PCR can, therefore, be a useful additional technique for the early diagnosis of M. tuberculosis infection, but it does not necessarily indicate active infection. Introduction Tuberculosis is a major cause of morbidity and mortality in developing countries. Moreover, the human im- munodeficiency virus (HIV) epidemic poses an additional risk factor for the progression of inactive (or dormant) tuberculosis to active disease. One of the principal reasons for the failure of tuberculosis control programmes in developing countries is the inability to detect infectious cases early enough, a Conventional methods for the laboratory diagnosis of tuberculosis have been very use- ful, but have serious limitations. 2 The Mantoux test is not very specific, while acid fast staining of sputum smears is not very sensitive. Culture of Mycobacterium tuberculosis is a more sensitive technique, but can take several weeks. The polymerase chain reaction (PCtl) is a rapid diagnostic technique which has the potential to overcome some of these limitations such as a lack of sensitivity and specificity. 3 Several studies on the use of PCR for the detection and identification of M. tuberculosis in clinical samples have been published. 4-1° In this study we aimed to evaluate the use of PCR of * Address all correspondenceto: M. van Staden. Accepted for publication 28 July 1997. serum samples for the diagnosis of tuberculosis, especially extrapulmonary infection. In these cases it is often difficult to obtain material from the site of infection for microscopic analysis, culture or PCR, while serum is easily obtainable using minimal facilities. A rapid blood-based diagnostic test for mycobacteria will also be of considerable benefit in circumstances where tuberculosis presents as an occult disseminated infection. Furthermore, in patients with the acquired immunodeficiency syndrome (AIDS) or other immunosuppressive disorders, giehl-Neelsen (ZN) stain- ing of sputum smears is less sensitive. I1 13 We report here the results of PCR on serum samples from 329 patients, and compare the results with their clinical diagnoses. Patients and Methods Clinical specimens Clotted peripheral blood samples were obtained from: (a) patients with proven tuberculosis infection either by ZN staining and/or culture positivity on Lowenstein-Jensen (LJ) slope, typical chest X-ray with positive Mantoux skin test, or increased adenosine deaminase (ADA) levels in body fluids (n= 78); and (b) from patients suspected of having tuberculosis based on clinical criteria (n=59) 0163-4453/98/030273 +05 $12.00/0 © 1998 The British InfectionSociety