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SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

Serosurvey among TB patients Sampling Design Sample size Timeframe Operational procedures Staffing and training Data collection and management Specimen collection and testing Data collection and management Quality assurance Measures to protect anonymity.

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SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

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  1. Serosurvey among TB patientsSampling Design Sample size Timeframe Operational procedures Staffing and training Data collection and management Specimen collection and testing Data collection and managementQuality assurance Measures to protect anonymity SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  2. Review of Design Options for HIV Surveillance • Passive surveillance of reports of HIV positive test results from laboratories, institutions, and hospitals where HIV testing is done • Active surveillance by population-based sample surveys or cross-sectional serosurvey • Studies such as seroincident cohort studies to monitor changes in HIV infection in identified individuals who return periodically for testing • Active surveillance of specific populations at sentinel sites using unlinked anonymous testing procedures • THIS IS RECOMMENDED AS THE BEST OPTION # 3-1-23

  3. Steps for Setting up an HIV Sentinel Surveillance System: General Survey Methods • Selection of sentinel populations • Selection of sample inclusion criteria • Selection of sites for sentinel surveillance • Review of methods for collecting blood samples • Review procedures for maintaining confidentiality • Determine data to be collected with blood samples • Determine methods for compilation, analysis, presentation, and dissemination of collected data at central and local levels # 3-A-3

  4. Considerations when selecting TB clinics • The selected TB clinics should not only be able to obtain the sample size needed for the serosurvey, but they should also be able to provide a national picture of the epidemic, which entails obtaining information from: • different geographical locations, including those with a high risk of HIV infection (e.g., borders, transport corridors); • areas with different population densities and sizes; • both urban clinics and rural clinics; • patients with different socioeconomic status. SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  5. Sampling terms Population: Group that is being sampled and targeted: TB patients Sample design: How a sample is selected from the population (e.g., convenience sample, simple random sample, cluster sampling with probability proportional to size) Sample unit: Unit for listing and selecting in a serosurvey (e.g., TB clinic, TB patients) Sample frame: List of all sample units from which a sample is drawn (e.g., list of all TB clinics, villages, or households in a province or country) SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  6. Criteria for selecting TB clinics • A reliable laboratory for processing of specimens and transport to the laboratory that will be conducting HIV testing. • The site is accessible to surveillance staff. • On-site staff members are willing to cooperate and are trained to conduct the serosurveys. • The site provides services to a sufficiently large number of clients. • On-site HIV counselling and testing services or referral to such services should be available to clients included in the serosurvey. SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  7. Steps for Setting up an HIV Sentinel Surveillance System: Laboratory Testing • Review recommended UNAIDS/WHO HIV testing strategy • Select HIV tests for surveillance • Develop HIV testing protocol for local and central level • Develop quality assurance plan for laboratory HIV testing at the central and local level # 3-A-5

  8. Steps for Setting up an HIV Sentinel Surveillance System • Budget for personnel and equipment needs • Plan for dissemination and presentation of results • National AIDS Committee • Ministry of Health/Government • Media and general public • Sentinel sites/districts/regions • High risk groups • Plan of action and timeline for implementation # 3-A-10

  9. Staffing • Local Level (clinic) • Clinic staff (nurse or laboratory technician) • Laboratory technician • Supervisory staff (nursing supervisor or senior laboratory technician) • Courier (someone from MOH or laboratory technician) • Regional Level • Laboratory technician • Survey Coordinator • National Level • Laboratory technician • Data manager/statistician • Surveillance coordinator # 3-6-3

  10. Steps for Setting up an HIV Sentinel Surveillance System: Training Requirements • Surveillance personnel • Sentinel site staff • Laboratory staff • Supervisory personnel • Data management and analysis personnel # 3-A-6

  11. Steps for Setting up an HIV Sentinel Surveillance System: Supervision of Surveillance Staff • Develop quality assurance plan for sentinel surveillance system • Sentinel sites • Laboratory quality assurance • Logistical issues • Data compilation, analysis, and presentation • Interpretation, use and feedback of results • District, regional, and national staff # 3-A-7

  12. Sampling in HIV Sentinel Surveillance • Definition of sampling • Sample size • Sampling methods • Duration • Frequency # 3-4-3

  13. Definition of Sampling Process of selecting and studying a representative subset of a larger population to estimate an unknown characteristic or parameter (in this case HIV prevalence) in that larger population # 3-4-4

  14. Sample SizeConsiderations • In general: Bigger is better! • Limited by: • time needed to reach sample size • financial resources • technical resources (workload for site staff, testing capacity, QA/QC…) # 3-4-5

  15. SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  16. Duration of Sampling Period • Trade off between volume at clinic and desired sample size • The shorter the better (preferably no more than 8 weeks, but this can be extended to 12 if necessary) # 3-4-16

  17. Frequency of Sampling • The financial, technical and human resources must be available at sentinel site • Conduct once a year • Areas of low prevalence (<2%) or generalised epidemics: every 1-2 years • Use: • Same sites • Same methods • Same time of year # 3-4-17

  18. Data Collection • Assure collection of information needed for surveillance • Assure that HIV test results cannot be linked to person • Use appropriately designed data forms • Data forms and lab specimens must be labeled with unique code unrelated to other identifiers # 3-7-2

  19. Flow of Data Collection Forms: Approach A Sentinel Site National Surveillance Program’s Data Manager Add demographic data to top portion of form; remove and send to Data Manager. Send lower portion to Laboratory. Regional/National Laboratory Add HIV test result to lower portion; send form to Data Manager Add demographic data Demographic data Add HIV test result HIV test result # 3-7-4

  20. Analysis and Interpretation of Data • Summarize results (frequency distribution, proportions, prevalence) for: • Entire survey sample • Each site • Each sub-group • Presentation of HIV prevalence by age groups especially helpful • HIV infection in younger persons may represent those with more recent infection • Trends in age groups over time # 3-7-7

  21. Prevalence of HIV in culture-confirmed TB patients (n = 4 639) * SA rate weighted by Province

  22. HIV prevalence (%) Prevalence of HIV in tuberculosis patients in the TB Centre in Chiangmai. Dots: observed; line: data fitted to a double logistic curve.

  23. Selection of Sentinel Sites:Conclusions • Goal is to eventually extend the number of sites to a broad distribution of geographic areas • However, number should not be unmanageable (resources should not be overextended) • It is better to have well conducted surveys in a few locations than to have poorly conducted surveys in many locations # 3-3-7

  24. Site Selection CriteriaRequirements • Sites provide services for selected sentinel populations • Blood is drawn from patients/clients as part of routine care or service provided at the site # 3-3-3

  25. Important Characteristics of Sentinel Populations • Definable and easily identified • Obtains health care or services at facilities that draw blood as part of the routine medical services • Minimises participation bias with unlinked anonymous testing • Readily accessible to surveillance staff # 3-2-3

  26. Sampling Methods: General Recommendation Of all three methods, consecutive sampling is recommended because selection bias is reduced and it is simple to execute # 3-4-15

  27. Unlinked Anonymous Testing (with informed consent) • Coded specimen • All personal identifiers removed • No counseling required • Used when specimens are collected solely for surveillance purposes # 3-5-8

  28. Specific HIV Testing Methods • Unlinked anonymous (with or without informed consent) • Linked confidential • Linked anonymous • Mandatory testing • Compulsory testing # 3-5-3

  29. Anonymous vs. Confidential Testing • Anonymous: No one knows who the patient is (staff can not identify individual with test results) • Confidential: Staff have access to patient identifying information but do not release information to anyone but patient # 3-5-4

  30. Linked vs. Unlinked Testing • With linked testing, specimen can be traced back to a patient’s chart (or personal identifying information) • With unlinked testing, bond between chart (or personal identifying information) and specimen is broken # 3-5-5

  31. Unlinked Anonymous Testing (without informed consent) • Coded specimen • All personal identifiers removed • No counseling required • Conducted in clinics where left-over blood (originally taken for other reasons, such as syphilis testing) can be tested for HIV surveillance purposes # 3-5-7

  32. Linked Confidential Testing (with informed consent) • Coded specimen • Code linked to personal identifier • Staff know specimen’s identity • Consent and counseling required • Useful when specimens are collected solely for HIV surveillance, for example, among populations not accessible through clinics (sex workers, drug users, men who have sex with men) # 3-5-9

  33. Linked Anonymous Testing (with informed consent) • No personal identifiers obtained • Coded specimen • Code given to patient • Consent and counseling required • Useful when specimens are collected solely for HIV surveillance among populations not accessible through clinics (sex workers, drug users, men who have sex with men) # 3-5-10

  34. Unlinked Anonymous Testing is Recommended for HIV Surveillance • Participation bias is reduced and therefore • accuracy is improved • Privacy is maintained • Logistically feasible and practical # 3-5-13

  35. The following information on site-specific characteristics should be gathered for each of the selected sites: • Number of patients per month as well as proportion who are repeat visitors • Age distribution of clients • Geographic locality of clinic (urban, semi-urban, rural) • Residence of clinic population (urban, semi-urban, rural) • Description of services provided at clinic (family planning, voluntary counselling and testing, prevention of mother-to-child transmission). SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  36. Steps for Setting up an HIV Sentinel Surveillance System: Equipment Needs • Specimen collection, serum separation, storage, and transport • Laboratory HIV testing • Supervision • Data compilation, analysis, and presentation • General office equipment and space needs # 3-A-9

  37. Site Selection CriteriaAccessibility • A reliable laboratory available on-site or nearby to perform the routine laboratory tests as well as processing the residual blood for later serologic HIV testing • Sites should be readily accessible to national-, regional- and district-level surveillance staff # 3-3-4

  38. Flow Chart of Unlinked Anonymous Testing # 3-5-15

  39. SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  40. Appropriate responsibilities for seroserveys personnel SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  41. Appropriate responsibilities for seroserveys personnel SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  42. Appropriate responsibilities for seroservey personnel SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  43. Maintaining motivation among serosurvey personnel •Develop a sense of serosurvey ‘ownership’ • Clearly define responsibilities and roles for all staff involved, at all levels • Emphasize the importance of each person’s contribution to the serosurvey’s success • Provide adequate staff training • Ensure that the necessary equipment is available to conduct the serosurveys • Assign certain data management and analysis responsibilities to regional coordinators. • Provide feedback on staff performance and serosurvey results SENTINEL SURVEILLANCE SYSTEMS Dr. GEORGE LOTH, SIR/HIV. NOV 2004

  44. HIV status according togender, previous TB treatment and drug resistance* * Results weighted by Province

  45. Sample Size Determinants • Margin of error = interval width around expected prevalence, e.g. +/-3% (i.e., for expected 10%, accept 7-13%) • Confidence limit (e.g., 90%, 95%, 99%): how confident you are that the true number lies within the interval you’ve measured • To calculate sample size, one can use the following formula*: N = 4 z² P (1- P) W² *Where z is the standard normal deviation for a two-tailed , where (1 - ) is the confidence level (for example, since  = .05 for a 95% confidence level, z = 1.96), P is the expected proportion of patients with the outcome, and W is the width of the interval. # 3-4-6

  46. Consecutive Sampling • Sample every eligible person (example: all women aged 15-49 at first visit) until sample size met or sampling period is complete • Less opportunity for error or unintentional manipulation # 3-4-12

  47. Systematic Sampling • Randomly select initial patient who meets eligibility criteria and then select every “Nth” (e.g. 3rd or 5th) eligible patient after that until the sample size is reached • More difficult to execute correctly - requires more attention to procedural detail # 3-4-13

  48. Random Sampling • Patients are selected at random (determined by random table or computer program) • Difficult to execute among multiple sites # 3-4-14

  49. How to Perform Unlinked Anonymous Testing • Specimen linked when originally taken • Performed in clinic setting where blood is collected regularly for other purposes (usually syphilis testing) • Sera are tested for HIV antibodies after the originally intended lab tests have been run • Personal identifiers removed • Coded with new, unlinked ID number • Collect variables such as age, sex, marital status, geographic area of residence, duration of stay in residence, and occupation # 3-5-14

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