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Example of Bias Matched Case-Control Study

Example of Bias Matched Case-Control Study. Lakkana Thaikruea MD., Cert of FETP, M.S., PhD. Department of Community Medicine, Faculty of Medicine, CMU. Risk Factors for Hepatitis C Virus infection among Blood Donors in Northern Thailand. Lakkana Thaikruea 1, Satawat Thongsawat 1,

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Example of Bias Matched Case-Control Study

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  1. Example of Bias Matched Case-Control Study Lakkana Thaikruea MD., Cert of FETP, M.S., PhD. Department of Community Medicine, Faculty of Medicine, CMU

  2. Risk Factors for Hepatitis C Virus infection among Blood Donors in Northern Thailand Lakkana Thaikruea 1, Satawat Thongsawat 1, Niwat Maneekarn 1, David L. Thomas 2, Dale Netski 2, Kenrad E. Nelson 2, 1 Departments of Community Medicine, Medicine, and Microbiology, Chiang Mai University, Chiang Mai, Thailand 2 Departments of Epidemiology & Medicine, Johns Hopkins University, Baltimore, USA

  3. Rationale • No effective program in Thailand to prevent HCV infection • Lack of information of majors route of transmission • Distribution of HCV genotypes are not well understood • Researchers from JHU and Chiang Mai University have conducted study about epidemiology of HCV in northern Thailand • Blood donor is one of the study population besides drug users, patients, and commercial sex workers • This present study focuses on blood donor

  4. Specific aims Blood donors in northern Thailand 1. To investigate the potential risk factors for HCV infection 2. To determine HCV genotype distribution 3. To investigate relationship between HCV genotype distribution and the routes of transmission

  5. Features of hepatitis C virus infection 15% 85% 80% 20% 75% 25%

  6. Background: Route of transmission USA: IDU1, sex with an IDU, blood transfusion among non-IDU REDS2:** male, black, 30 to 49 years, < high school diploma, first /only time blood donor, blood transfusion history 1 Injection drug users ; 2 Retrovirus Epidemiology Donor Study

  7. Specific aim 1 To investigate the potential risk factors for HCV infectionamong blood donors in northern Thailand

  8. Methods: Specific aim 1 • Setting • Design • Data collection • Data analysis

  9. Methods (cont.) • Faculty of Medicine, CMU • The Blood Bank - The Maharaj Nakorn Chiang Mai hospital - 1,800-bed capacity and the main referral center • Blood donors • January 2001 - June 2002 • ≥ 18 years old at the time of donation/ recruitment • Reside in the north • Donation sites: walk-in and mobile unit Study setting

  10. Methods (cont.) Single masked matched case- control • Matched variables: age, gender, donation date, donation sites • Mask: interviewers and physicians did not know HCV status of the participants Study design: Specific aim 1

  11. Data collection Eligible Case: blood bank EIA-3 positive • Invitation letters: 2nd letter in 2 weeks apart • Non-participants: sent their participation forms indicating their unwillingness • Enrolment: explain, consent form • Trained health personnel of the same gender: face-to-face interview • Physical examination • Counseling • Laboratory tests: 30 ml blood • HCV antibodies; EIA-3, RIBA-3 • HCV RNA: RT-PCR • HCV genotypes: direct sequencing • Serum ALT

  12. Data collection (cont) Eligible cases were defined as “confirmed cases ” If they were HCV EIA-3 positive in blood bank screening and had any of the following: • PCR positive, or • PCR negative with RIBA-3 positive, or • PCR negative with both • positive high cut-off repeat EIA-3 (Abbot) • positive high cut-off repeat EIA-3 (Ortho)

  13. Data collection (cont.) Eligible Control: blood bankEIA-3 negative • Randomly selection: • 1 – 4 eligible controls per case • Matched variables: • ± 15 days of case’s donation date • Age ± 5 years old • Same gender • Same donation sites • Enrolment: same • Control: • Negative to both screening EIA-3 and repeat EIA-3

  14. Data collection (cont.) SPOUSES • Spouses of cases and matched controls • Regular sexual relations with the donor for ≥ 3 months • ≥ 18 years old at the time of recruitment • Enrolment: same • HCV infection: • EIA-3 positive and • Either PCR or RIBA-3 positive

  15. Flow of matched case-control study 38,340 donors 102 low cut-off EIA-3 positive 28 not eligible EIA-3 positive 372 EIA-3 pos Eligible cases 372 eligible cases 1234 eligible matched controls 618 non-responders 85 returned letters 903 responders 238 non-participants 67 false positive cases 12 RIBA-3 indeterminate 82 matched controls 9 cases without control

  16. Participation • Compared between participants and non-participants • Cases: 254 participants (91.4%) versus 24 non-participants • No statistically significant different • Controls:411 participants (65.8%) versus 214 non-participants • Participants: age in years 33.2 ( VS 31.0)* • Participants: ever donated 81.6 % (VS 61.3 %)* * P value < 0.05

  17. Data analysis: Specific aim 1 • Univariate analysis • Matched odds ratio (OR) with 95% confidence interval (95% CI) • Multivariate analysis • Conditional logistic regression • Step-wise selection: • alpha levels of 0.05 for entry and 0.0501 for remove • to guide the selection of variables • Either independent variables that were likely confounders or had biological importance were forced in to the preliminary model regardless of their statistical significance • Phylogenic analysis 1 • Tree was constructed from nucleic acid sequence alignments using Neighbor joining method • Sequence alignments were randomly permuted 1,000 times • CONSENSE provided bootstrap values • Reference sequences: GenBank • programs: Gofasta1.1, BioEdit 5.9, Tree View 1.6 , PHYLIP 3.572c package ( SEQBOOT, DNADIST, NEIGHBOR, CONSENSE)

  18. Results: Specific Aim 1 • Demographic distribution • Multivariate • Spouses

  19. Limitations: Specific aim 1 Limitations: -causal relationship; temporal ambiguity - spouses; might not represent

  20. Strengths: Specific aim 1 - appropriate study design; • sample size • matched case-control • confounding - minimized selection bias; • asymptomatic nature • lacked HCV knowledge • available of HCV test only in some secondary or tertiary cares • self-deferral system - minimized information bias; • masked • face-to-face interview • physical examination - minimized misclassification of HCV status; • confirmatory tests

  21. Publications • The risk factors for HCV infection among blood donors in northern Thailand: Matched case-control study. Presenter: Lakkana Thaikruea (The XV International AIDS Conference. July 10-16, 2004. Bangkok, Thailand) • Risk Factors for Hepatitis C Virus Infection Among Blood Donors in Northern Thailand Lakkana Thaikruea1,6, Satawat Thongsawat3,6, Niwat Maneekarn4,6, Dale Netski 5, David L. Thomas ,5 Kenrad E. Nelson2 (Transfusion, 2004 - in process)

  22. Other Related Publications • Epidemiology of hepatitis C virus infection among blood donors in northern Thailand Presenter: Lakkana Thaikruea (InternationalCenters for Tropical Disease Research Network, 12th Annal Meeting, May 13-15, 2003, NIH, Bethesda, MD, USA) • Relationship between HIV and Hepatitis C Viral Genotypes and Routes of Transmission among Blood Donors in Northern Thailand. Presenter: Lakkana Thaikruea) (11th CROI retrovirus and Opportunistic Infection Conference, Feb 7-11, 2004, San Francisco, CA , USA)

  23. Khop Khun Krup

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