unit 5: specialised techniques: sti prevalence assessment and combined sti/hiv behavioural...

Unit 5: Specialised Techniques: STI Prevalence Assessment

and Combined STI/HIV Behavioural Surveillance

Surveys

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Warm Up Questions: Instructions

Take five minutes now to try the Unit 5 warm up questions in your manual.

Please do not compare answers with other participants.

Your answers will not be collected or graded.

We will review your answers at the end of the unit.

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What You Will Learn

By the end of this unit you should be able to:

discuss the use of prevalence assessment in a comprehensive STI surveillance system

discuss how STI sero-prevalence studies can be linked to HIV sero-prevalence studies

discuss the assessment of STIs in serological surveys

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What You Will Learn, Cont.

By the end of this unit you should be able to:

discuss how prevalence assessment studies can be linked to behavioural surveillance surveys

identify the STIs most suitable for inclusion in combined STI/HIV behavioural surveillance studies

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Prevalence Assessment and Monitoring

A component of STI surveillance similar to sero-prevalence surveys. It is either: part of a combined HIV/STI behavioural survey part of a national HIV sero-prevalence survey a stand-alone project

STIs that are usually included are: syphilis gonorrhoea chlamydia

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Choosing STIs for Behaviour Surveys

Objectives: Identify population sub-groups with high STI

prevalence Monitor trends in STI prevalence among defined

populations

Uses: Interventions (screening, treatment) To obtain data for programme planning Detection and treatment of STIs among routinely

screened populations (such as pregnant women)

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Definitions and Terms

Prevalence: proportion of people in a population who have a disease or infection at a specified time

Prevalence monitoring: following prevalence trends over time to see if they are increasing or decreasing

STI prevalence assessment and monitoring: using surveys to determine what percentage or how many people have STIs when compared to the total population

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Programme Planning

STI prevalence data can be used to: develop national estimates of STIs

identify population sub-groups at high risk for HIV infection

guide funding and resource allocation for STI and HIV prevention programmes

monitor effectiveness of STI and HIV prevention programmes

intervene in the transmission of STI through screening and treatment

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General Population Surveys

Serological screening among the general population is usually done in: Antenatal clinics, at least every two years Blood donations, where anonymous STI data

should be passed to STI programmes

Routine testing is also done in: Prisoners at entry to detention facilities Military recruits Routine sex worker examinations

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General Population Surveys, Cont. These are usually relatively unbiased.

They are used to guide STI/HIV programmes.

These are different from surveys at sentinel sites, which provide more complete data.

Types of tests that can be done include: Sero-prevalence surveys for syphilis Urine screening for chlamydia and gonorrhoea Sero-prevalence surveys for herpes and hepatitis

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Figure 5.1. Calculating Prevalence

Calculating prevalence:

Prevalence =

Total number of patients who test positive for a specific disease

Total number of patients tested

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Figure 5.2. Calculating Syndromic Prevalence

Calculating syndromic prevalence (when testing equipment is not available):

Syndromic prevalence =

Total number of patients displaying symptoms for a

specific disease

Total number of patients seen

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Analysis of STI Prevalence Data

Quarterly and annual trends should be analysed overall and stratified by basic categories, such as: Disease Sex Age group Geographic location

Changes in prevalence may be due to: Different types of clinics Changes in health-seeking behaviours Changes in selection criteria of patients Changes in diagnostic tests

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Combined STI/HIV Behavioural Surveillance Surveys

These surveys combine: STI/HIV prevalence assessments –

measure the proportion of a population that has a particular disease

behavioural surveys – use questionnaires to examine the prevalence of behaviours associated with HIV transmission

Combining surveys reduces costs.

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Goals of Combined STI/HIV Behavioural Surveillance Surveys

Assess prevalence of asymptomatic STIs Identify population sub-groups at high risk for HIV Assess health-seeking behaviour for STI services Measure the effectiveness of HIV/STI prevention

programmes Determine the need for additional services Guide funding and resource allocation

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What is Involved

Data elements for behavioural surveillance include: Number of sexual partners in past 3 or 12 months New sexual partners in past 3 months Condom use Alcohol or drug use in past 12 months Giving or receiving money for sex in past 12 months

Data collection for prevalence assessments is done using blood or urine tests.

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Which STIs Should You Test For?

Factors to consider: Laboratory infrastructure in country Type of populations under study

The table on the following page describes which STI testing is most appropriate for each type of population sub-group.

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Table 5.1. Populations and STI Monitoring

Population STI CommentsLow-risk (youth) HSV-2, N. gonorrhoeae,

C. trachomatisHSV-2 measures early sexual exposure

Bridging and high-risk such as:sex workerstruck driversinjection drug users

N. gonorrhoeae, C. trachomatis, H. ducreyi, T. vaginalis

Measures recent sexual exposure

T. pallidum Exposure period cannot be determined unless titres are used

General population N. gonorrhoeae, C. trachomatis

Measures recent sexual exposure

T. pallidum Exposure period cannot be determined unless titres are used

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Data Elements

The data collected depends on population surveyed. For example: High-risk groups: more attention is given to

specific high-risk behaviours. General population: demographic

characteristics, health-related behaviours and general risk questions are given priority.

Denominator data are also collected.

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Data Analysis

Initially analyse STI data separately:

Count gonorrohea and syphilis cases separately.

Calculate prevalence and risk factors for each disease separately.

Calculate prevalence according to demographic variables for each disease separately.

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Reporting Results of Special Studies

People experienced in health communications should design materials.

The report should be distributed to: National AIDS/STI programme directors District medical officers Healthcare providers Non-governmental organisations Donors Other public health agencies

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Types of Reports

Annual STI surveillance reports

Fact sheets for health department offices and clinics

Regular newsletters for clinicians and laboratory personnel

Press releases

Educational materials

Verbal feedback during meetings and supervisory visits

Electronic media

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In Summary

STI prevalence assessments can be used to monitor STI prevalence trends in population sub-groups.

Combined STI/HIV and behavioural surveys allow surveillance officers to calculate STI prevalence among high-risk groups.

Selecting an STI for inclusion in a combined STI/HIV behavioural surveillance study depends on the population surveyed and laboratory infrastructure.

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Warm Up Review

Take a few minutes now to look back at your answers to the warm up questions at the beginning of the unit.

Make any changes you want to.

We will discuss the questions and answers in a few minutes.

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http://www.who.int/en/

Answers to Warm Up Questions

1. Prevalence ____________ is the determination of prevalence among persons screened in defined populations, while prevalence monitoring is the determination of trends in prevalence over time.

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Answers to Warm Up Questions

1. Prevalence assessment is the determination of prevalence among persons screened in defined populations, while prevalence monitoring is the determination of trends in prevalence over time.

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Answers to Warm Up Questions, Cont.

2. True or false? STI prevalence data that show high rates of STIs are used to identify population sub-groups at high risk for HIV infection.

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2. True or false? STI prevalence data that show high rates of STIs are used to identify population sub-groups at high risk for HIV infection. True

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3. What is the primary purpose of STI prevalence assessment and monitoring?

a. to identify population sub-groups with high prevalence of STIs

b. to monitor trends in STI prevalence among defined populations

c. a and b

d. none of the above

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3. What is the primary purpose of STI prevalence assessment and monitoring?

a. to identify population sub-groups with high prevalence of STIs

b. to monitor trends in STI prevalence among defined populations

c. a and b

d. none of the above

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4. In an STI prevalence survey of the general population, which STIs would you test for?

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4. In an STI prevalence survey of the general population, which STIs would you test for? Gonorrhoeae, chlamydia, syphilis

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5. True or false? Undertaking a combined STI/HIV prevalence assessment and behavioural surveillance survey can identify population sub-groups at high risk for HIV infection.

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5. True or false? Undertaking a combined STI/HIV prevalence assessment and behavioural surveillance survey can identify population sub-groups at high risk for HIV infection. True

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6. True or false? The choice of which STI to include in a behavioural survey is made independently of the type of population to be studied.

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6. True or false? The choice of which STI to include in a behavioural survey is made independently of the type of population to be studied. False

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7. True or false? STI prevalence data are useful for monitoring the effectiveness of HIV prevention programmes.

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7. True or false? STI prevalence data are useful for monitoring the effectiveness of HIV prevention programmes. True

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8. True or false? Combining HIV/STI surveillance and behavioural surveillance surveys is more cost effective than conducting the two surveys separately.

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8. True or false? Combining HIV/STI surveillance and behavioural surveillance surveys is more cost effective than conducting the two surveys separately. True

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9. What does X represent in the equation below?

a. total number of patients who test negative for a specific disease

b. total number of patients who test positive for all priority diseases

c. total number of patients tested

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Prevalence =


X


9. What does X represent in the equation below?

a. total number of patients who test negative for a specific disease

b. total number of patients who test positive for all priority diseases

c. total number of patients tested

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Prevalence =


X

Small Group Discussion: Instructions

Get into small groups to discuss these questions.

Choose a speaker for your group who will report back to the class.

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Small Group Reports

Select one member from your group to present your answers.

Discuss with the rest of the class.

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Case Study: Instructions

Try this case study individually.

We’ll discuss the answers in class.

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Case Study Review

Follow along as we go over the case study in class.

Discuss your answers with the rest of the class.

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Questions, Process Check

Do you have any questions on the information we just covered?

Are you happy with how we worked on Unit 5?

Do you want to try something different that will help the group?

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unit 5: specialised techniques: sti prevalence assessment and combined sti/hiv behavioural...

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