Risk of tuberculosis in patients with rheumatoid arthritis in Hong Kong--the role of TNF blockers in an area of high tuberculosis burden.
OBJECTIVE
To elucidate the incidence rate and relative risk of tuberculosis (TB) in patients with rheumatoid arthritis (RA) compared to the general population in Hong Kong between 2004 and 2008, and to assess whether this risk is associated with exposure to tumour necrosis factor (TNF) blockers after adjusting for other known risk factors.


METHODS
We reviewed all the medical records of RA patients to determine the standardised incidence ratio (SIR) of TB in RA patients. Independent explanatory variables associated with active TB in RA were ascertained using the Cox regression model.


RESULTS
A total of 2441 RA patients followed at the 5 centres were recruited. The mean age at the start of follow up was 56±14 years. The median follow-up duration was 6,616 and 185 patient-years for the TNF naive and TNF treated groups, respectively. Compared to age- and sex-matched population controls, the SIR of active TB in RA was significantly increased (SIR for TNF naïve RA: 2.35, 95% CI 1.17-4.67, p=0.013, SIR for TNF treated RA: 34.92, 95% CI 8.89-137.20, p<0.001). Independent explanatory variables associated with an increase risk of active TB included older age at study entry (RR 1.05, p=0.013) a past history of pulmonary TB (RR 5.48, p=0.001), extra-pulmonary TB (RR 16.45, p<0.001), Felty's syndrome (RR 43.84, p=0.005), prednisolone>10mg daily (RR 4.44, p=0.009) and the use of TNF blockers (RR 12.48, p<0.001).


CONCLUSIONS
Exposure to TNF blockers remained to be an independent risk factor for TB in RA after adjusting for other known risk factors.
Tam
L-S
LS
Department of Medicine and Therapeutics, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong. tamls_813@yahoo.com
Leung
C-C
CC
Ying
S K
SK
Lee
G K
GK
Yim
C-W
CW
Leung
Y-Y
YY
Kun
E W
EW
Wong
K-K
KK
Li
E K
EK
D000911:Antibodies, Monoclonal / Q000009:adverse effects* / Q000276:immunology; D018501:Antirheumatic Agents / Q000009:adverse effects* / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000453:epidemiology*; D015897:Comorbidity; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D016867:Immunocompromised Host; D007165:Immunosuppression Therapy; D007166:Immunosuppressive Agents / Q000009:adverse effects* / Q000276:immunology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D014376:Tuberculosis / Q000453:epidemiology* / Q000209:etiology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*
D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D007166:Immunosuppressive Agents; D014409:Tumor Necrosis Factor-alpha