Percentage of newly registered TB patients who are HIV positive
Surveillance of HIV prevalence among TB patients will give information about the epidemics of both TB and HIV. In particular, it indicates the degree of overlap in the epidemics in any given setting and, when compared with the HIV prevalence in the general population, indicates the contribution of HIV to the TB epidemic in any given setting.
Total number of newly registered TB patients who are HIV positive over a given time period
Total number of newly registered TB patients (registered over the same given time period) who were tested for HIV and included in the surveillance system
Numerator / Denominator
Selecting the appropriate strategy for HIV surveillance among TB patients depends mainly on the existing surveillance system and the underlying HIV epidemic state in a country. There are three main methods
for surveillance of HIV among TB patients.
Routine HIV testing data can form the basis of a reliable surveillance system at all levels of HIV epidemic (low-level, concentrated and generalized), provided that high coverage is achieved (more than 80 percent of all TB patients giving consent and being tested). These routine data can be calibrated by periodic (special) or sentinel surveys. Sentinel surveillance collects information regularly and consistently from a predetermined number of people from speciﬁc sites and population groups that are of particular interest or are representative of a larger population. The difﬁculty with sentinel surveillance is in determining how representative the people are of the population from which they are taken and how representative they are of the general population of
TB patients. Sentinel surveillance systems are usually based on unlinked anonymous testing methods, often using blood specimens that have been collected for other purposes and stripped of all identifying markers.
Periodic special surveys have a speciﬁc role in which the prevalence of HIV among TB patients has not been previously estimated and are an essential part of the initial assessment of the situation. Surveys using
representative sampling methods and appropriate sample sizes can provide accurate estimates of the burden of HIV among TB patients. This information may alert TB programs to a potential HIV problem and enable
action to be taken that may include the implementation of more systematic surveillance.
Surveillance of HIV prevalence should ideally include all newly registered TB patients, diagnosed according to international standards. However, if periodic special surveys or sentinel methods are used and resources are limited, countries may choose to include only adults with smear-positive pulmonary TB: those with a deﬁnitive diagnosis of TB. Countries with scarce resources in which the HIV epidemic state is either low or concentrated may also choose to only include a smaller subgroup of TB patients, such as adults aged 15–59 years.
Relapse cases should be excluded from surveillance systems because of the risk of surveying the same patient twice, unless they are identiﬁed as such and the results are analyzed separately. However, relapse
cases may be included and need not be identiﬁed as such if surveillance is based on survey methods and these surveys are undertaken over a short period of time, ideally less than 2–3 months.
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HIV status: N/A
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