The Second Global Symposium on IGRAs June 1, 2009

Transcription

1 Akiko Kowada, MD PhD Director, Department of Health Service Katsushika City Public Health Center, Tokyo, Japan The Second Global Symposium on IGRAs June 1, 2009

2 Overview Background Study 1: Cost effectiveness of IGRAs for tuberculosis contact screening Study 2: Cost effectiveness of IGRAs for annual tuberculosis healthcare worker screening

3 Incidence of TB (2006)

4 Notification rates of TB in Japan Notification rate smear positive pulmonary tuberculosis

5 Recent Epidemiology of TB in Japan (2007) BCG vaccination 97.4 % Newly notified patients 25,311 Notification rate 19.8 / 100,000 Death due to TB 1.7 / 100,000 Success of TB treatment 46.4 %

6 Study 1: Cost Effectiveness of IGRAs for Tuberculosis Contact Screening

7 Objective My aim is to perform the cost effectiveness of the QFT(QuantiFERON TB Gold) compared with the TST (the tuberculin skin test ) for tuberculosis contact screening in Japan.

8 Methods Target population : 20 years old close contacts of patients with sputum smear positive tuberculosis Main outcome measure : Incremental cost per Quality adjusted life year (QALY) gained during lifetime Annual discount rate : 3%

9 Three strategies for TB contact screening Suspect LTBI TST alone strategy TST followed by QFT strategy QFT alone strategy LTBI=latent tuberculosis infection

10 Clinical state-transition diagram MDR=multidrug resistant

11 Baseline value and Range(1) Value Lower Upper Probability of having LTBI Sensitivity / Specificity of QFT Sensitivity / Specificity of TST (erythema) Adherence rate of Chemoprophylaxis Probability of MDR-TB in new TB cases 0.76/ / / / / /

12 Baseline value and Range(2) 1$=124yen(2006) Value Lower Upper TST per one shot ($) QFT diagnostic kit ($) Chemoprophylaxis by INH for 6 months ($) Treatment of INH-induced hepatitis ($) TB treatment for 6 months ($) Treatment for MDR-TB ($)

13 Results Incremental cost effectiveness of strategies Base case Age 20 years Cost $ QALYs Incremental cost effectiveness ratio QFT alone strategy TST /QFT strategy (+29.01) ( ) Dominated TST alone strategy (102.44) ( ) Dominated

14 One way sensitivity analysis on TST specificity P_TST_10_spe = TST specificity

15 Cost effectiveness acceptability curves Specificity of TST: Proportion cost-effective y 40y 20y 95% chance of being cost effective:$72,000 95% chance of being cost effective:$65, Willingness to pay, $

16 Conclusion (Study 1) 1.The QFT alone strategy is the most cost effective for TB contact screening in Japan. 2.When the TST specificity is over 0.72, the TST followed by the QFT strategy is more cost effective than the QFT alone strategy at the level of $US 25,000/QALY gained as a willingness to pay. 3. The QFT alone strategy would be more cost effective in individuals at high risk of tuberculosis mortality, such as the elderly.

17 Study 2: Cost Effectiveness of IGRAs for Annual Tuberculosis Healthcare worker Screening

18 Objective My aim is to perform the cost effectiveness of the QFT compared with the TST for annual tuberculosis screening of healthcare workers in Japan.

19 Methods Target population : 20 years old healthcare workers Main outcome measure : Incremental cost per Quality adjusted life year (QALY) gained during lifetime Annual discount rate : 3%

20 Three strategies for annual TB healthcare worker screening Suspect LTBI ２ step TST followed by Chest X ray strategy QFT followed by Chest X ray strategy QFT alone strategy

21 Clinical state-transition diagram

22 Baseline value and Range(1) Value Lower Upper Probability of showing evidence of TB by chest X-ray on the first year Probability of becoming QFT positive on the next year Probability of having LTBI Recurrence to TB after treatment Sensitivity / Specificity of QFT 0.76/ / /0.99 Sensitivity / Specificity of TST (cut-off 15mm) 0.5/ / /0.9

23 Baseline value and Range(2) 1$=98yen(2008) Value Lower Upper TST per one shot ($) QFT diagnostic kit ($) Chemoprophylaxis by INH for 6 months ($) Treatment of INH-induced hepatitis ($) TB treatment for 6 months ($) Contact screening ($)

24 Results Incremental cost effectiveness of strategies Base case Age 20 years QFT alone strategy QFT /Chest X-ray strategy 2 step TST /Chest X-ray strategy Cost $ QALYs 3, , (+41.91) 3, ( ) (-0.037) (-0.055) Incremental cost effectiveness ratio Dominated Dominated

25 p_tb_next year=probability of becoming TB on the next year p_infected_tb=probability of having LTBI p_qft_positive_nextyear=probability of becoming QFT positive on the next year senqft=sensitivity of QFT p_adherence_inh=adherent rate of INH prophylaxis

26 One way sensitivity analysis on probability of having LTBI p_infected_tb=probability of having LTBI

27 Conclusion (Study 2) 1. The QFT alone strategy is the most cost effective in BCG vaccinated healthcare workers in Japan. 2. When the probability of having LTBI is over 0.463, the QFT/Chest X ray strategy is more cost effective than the QFT alone strategy at the threshold of $US25,000/QALY as a willingness to pay.

28 Acknowledgements Tsuguya Fukui, MD PhD MPH President, St Luke s International Hospital, Tokyo, Japan Takuro Shimbo, MD Director, International Clinical Research Center, Research Institute, International Medical Center of Japan Osamu Takahashi, MD PhD MPH Senior Staff, St Luke s International Hospital, Tokyo, Japan

29 Thank you very much for your kind attention! a-kowada@city.katsushika.lg.jp