Biomarkers are objective physical or biologic measures of health conditions. For years, DHS surveys have gathered data on height and weight to evaluate nutritional status of women and children. Now, using field-friendly technologies, MEASURE DHS is able to collect biomarker data relating to a wide range of health conditions, including infectious and sexually transmitted infections (STIs), chronic illnesses (such as diabetes, micronutrient deficiencies), and exposure to environmental toxins.
Traditionally, much of the data gathered in DHS surveys is self-reported. Biomarkers complement this information by providing an objective profile of a specific disease or health condition in a population. Biomarker data also contribute to the understanding of behavioral risk factors and determinants of different diseases.
Measuring Biomarkers
The demand for biomarker data is growing worldwide. In 1995, anemia testing became a standard component of the DHS survey protocol after the Kazakhstan DHS showed that respondents were comfortable with providing blood specimens for testing. Since then, 15 more biomarkers have been added to DHS surveys in more than 30 countries. DHS surveys have tested for syphilis, the herpes simplex virus, HIV, serum retinol (Vitamin A), lead exposure, high blood pressure, and immunity from vaccine-preventable diseases, such as measles and tetanus. Most surveys now include testing for HIV infection in their survey design.
MEASURE DHS uses field-friendly equipment and rapid testing technologies whenever possible to get results quickly and reliably. Many tests can be carried out using only a few drops of blood from a finger or heel. With the development of portable analyzers, the results of some tests, such as anemia, and referrals for treatment can be provided to the respondent within minutes. Other tests still require specimens to be transported to the laboratory for analysis. Dried blood spots (DBS) on filter paper are increasingly used for many tests, including HIV. This method of specimen collection has eliminated the need for cold chain and/or refrigeration of specimens, reducing considerably the complexity of storage in the field and transport to the laboratory.
Using Biomarker Data
Biomarker data provide much needed information about the prevalence of health conditions, such as anemia or STIs. With this information, public health specialists can:
Identify risk factors for certain conditions;
Track trends in prevalence over time;
Identify the health care needs in different population groups and areas;
Evaluate the impact of health promotion and service delivery interventions;
Improve training for health care providers; and
Develop advocacy materials and interventions based on objective data.
DHS Data at Work
HIV Prevalence Rate
HIV prevalence data collected in a number of DHS surveys are helping policymakers and HIV/AIDS program managers to plan for prevention and treatment interventions. In Kenya, HIV estimates derived from HIV testing in the 2003 Kenya DHS led the government to adjust the official HIV prevalence rate. Further, based primarily on the HIV data from its 2005 to 2006 National Family Health Survey (NFHS-3), the Government of India revised its official estimate of persons living with HIV from 5.2 million to 2.47 million, which led to a major reduction in the UNAIDS global estimates of persons living with HIV. Ethiopia is another example of a country that revised its HIV estimates based on DHS data.
Anemia Prevention Programs
DHS surveys in Kazakhstan, the Kyrgyz Republic, Turkmenistan, and Uzbekistan were instrumental in influencing national policy on programs to combat anemia. Anemia testing in these four countries found high levels of anemia among women and young children. Between 23 and 30 percent of children younger than three years old were moderately or severely anemic, while 9 to 15 percent of women suffered from moderate or severe anemia. In response to these findings, these Central Asian governments have introduced anemia prevention programs, including iron supplementation and wheat flour fortification.
