Tuberculosis prophylaxis in patients with steroid treatment and systemic rheumatic diseases. A case-control study

B. Hern&aacutendez-Cruz¹, S. Ponce-de-Le&oacuten-Rosales², J. Sifuentes-Osornio³, A. Ponce-de-Le&oacuten-Gardu&ntildeo³, E. D&iacuteaz-Jouanen<sup>4

1</sup>Department of Internal Medicine; ²Department of Internal Medicine and Clinical Epidemiology; ³Department of Infectious Diseases; ⁴Teaching Division, Instituto Nacional de la Nutricion Salvador Zubiran, Mexico D.F., Mexico


ABSTRACT
Objective
The aim of this study was to assess the impact of isoniazid prophylaxis in patients with systemic rheumatic diseases who attended a teaching hospital in Mexico City between 1987 and 1992.

Methods
In this case-control study, patients with systemic rheumatic diseases and tuberculosis (cases) were compared with patients with systemic rheumatic diseases without tuberculosis (controls). The groups were matched by year of hospital admission and rheumatic disease. Clinical charts were reviewed for: 1) isoniazid prophylaxis, defined as the administration of isoniazid 300 mg/day for 6 or more months in patients with exposure to steroids (prophylaxis with isoniazid was defined as complete, incomplete or any prophylaxis); 2) exposure to steroids: defined as the administration of prednisone > 15 mg/day (or its equivalent of another steroid) for 3 or more months before tuberculosis or recruitment into the study; 3) exposure to immunosuppressants, defined as the administration of any dose of azathioprine, methotrexate, cyclophosphamide, and/or 6-mercaptopurine, before tuberculosis in the cases or recruitment date in the controls; 4) reactivity to PPD; and 5) other relevant variables.

Results
Twenty cases and 66 controls were studied. A 70% decrease in the risk of developing tuberculosis was found among patients who received any prophylaxis with isoniazid as compared to controls: OR 0.31, 95% CI 0.09 - 0.98, p = 0.03. A 97% decrease was seen in those patients who received complete prophylaxis: OR 0.034, 95% CI 0.0001 - 0.216, p <0.0001. The protective effect of complete prophylaxis persisted even after controlling for other potential confounders, such as age, gender, rheumatic disease, duration of rheumatic symptoms, and exposure to steroids and/or immunosuppressants.

Conclusion
The results of this study suggest that in countries with a high prevalence of tuberculosis the use of isoniazid (300 mg/day for 6 months) in rheumatic patients with exposure to prednisone (> 15 mg/day for three or more months) may be useful to prevent tuberculosis, independently of the results of the PPD reactivity test. However, a controlled clinical trial will be required to confirm these results.

Key words
Tuberculosis, SLE, rheumatic diseases, prophylaxis, isoniazid.

Blanca Hernandez-Cruz, MD, Rheumatologist, Staff Researcher; Sergio Ponce-de-Leon-Rosales, MD, MSc, Staff Researcher, Clinical Epidemiologist; Jose Sifuentes-Osornio, MD, Infectologist, Staff Researcher; Alfredo Ponce-de-Leon-Garduno, MD, Infectologist, Staff Researcher; Efrain Diaz-Jouanen, MD, FACR, FACP, Chairman.

Please address correspondence and reprint requests to: Efrain Diaz Jouanen, MD, Teaching Division, Instituto Nacional de la Nutricion Salvador Zubiran, Vasco de Quiroga no. 15, D.F. Mexico CP 14000, Mexico.

Received on May 22, 1998; accepted in revised form on October 13, 1998.

Clinical and Experimental Rheumatology 1999; 17: 81-87.
© Copyright Clinical and Experimental Rheumatology 1999.