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In European Biopharmaceutical Review, CHS Researcher describes realities of using diagnostic tests in developing countries

Manuel Silva, a volunteer community heath worker in the Peruvian Amazon, is one of a cadre of health workers recruited by the Peruvian Ministry of Health in the mid-1990s to provide malaria diagnostic services in remote areas.

In an article published in the October 2009 European Biopharmaceutical Review (EBR), Dr. Steven Harvey, a senior researcher with URC and CHS, tells Manuel’s story to illustrate the challenge that infectious disease diagnosis presents in the developing world.

Manuel risks losing crops to provide the community with diagnostic services

Manuel was trained to prepare blood slides
for malaria diagnosis, but not trained to read them. He must travel an hour and a half to reach the nearest facility with a microscope and a technician trained to use it. Add the time to prepare a slide and the wait for the bus, and Manual, a farmer, has lost half a day’s work in the field. In high transmission season when Manuel sees many patients each week, he risks losing his crops leaving his family with nothing to eat.

Test developers must take real work conditions into account

Harvey served as principle investigator for Diagnostic Cost Analysis for the Developing World, a CHS project funded by the Bill and Melinda Gates Foundation. The project team evaluated the potential market for new rapid diagnostic tests for the infectious diseases—HIV/AIDS, TB, malaria, sexually transmitted infections, and acute lower respiratory infections—that disproportionately affect developing countries.

In the EBR article, Harvey details the factors that must be taken into account when developing diagnostic tests and suggests steps that can be taken to help end-users.

Waiting for a diagnosis

Primary care facilities, while closest to most patients, may lack even the most basic services, such as electricity and running water. With poor or non-existent roads, travel to the nearest health post could take days, Harvey notes. Patients in communities in the region with the highest malaria incidence may wait from 3.7 days to as long as nine days for their test results.

Syphilis screening for pregnant women in Tanzania illustrates the challenge infectious disease diagnosis presents

A study of pregnant women attributed 51% of stillbirths, 24% of preterm live births, and 17% of adverse pregnancy outcomes to maternal syphilis. Although Tanzania’s national policy calls for all women receiving antenatal care to be routinely screened for syphilis, the screening is far from universal. The need for refrigeration of the reagents and agitation of the test card makes widespread screening difficult. In locations lacking electricity or a rotator machine, nurses must rotate tests by hand. 

TB testing even more challenging 

Most developing countries rely on a combination of sputum smear microscopy and non-specific clinical symptoms for initial diagnosis of tuberculosis (TB), Harvey points out. Health care providers use cultures to diagnose multi-drug resistant (MDR) TB, a lengthy and expensive process that few laboratories in developing countries can perform.  As a result, many countries perform drug susceptibility testing only after treatment failure with first-line drugs. Another three to four months pass before MDR-TB is suspected, during which time, the patient remains contagious with continuing health deterioration.

Urgent need for practical point-of-care diagnostics

With the possible exception of TB, effective diagnostic tests exist for all these conditions, but many tests cannot be used in the settings where the diseases are the most prevalent: They are blocked by barriers such as cost, infrastructure, logistics, human resources, and quality control. If new approaches are to be effective, Harvey recommends, they must take into account that the environment in which they will be used is very different than that of a sophisticated laboratory in an industrial setting.

The World Health Organization (WHO) recommends that new tests be developed that are affordable, sensitive, specific, user-friendly, robust, rapid, equipment free, and deliverable to those who need them. Recognizing the realities of using these tests in developing country settings, Harvey adds several practical recommendations. He notes that the tests “should: 1) have a shelf-life long enough to remain viable through months of transportation and storage; 2) be reagent-free or use low-cost reagents which are readily available; 3) be heat and humidity stable to around 45°C; and 4) ideally, depend upon a non-invasive sample, such as urine or saliva.”

RDTs provide a partial solution but much work is still needed

Point-of-care diagnostics are essential where residents live far from even the most basic health facility, Harvey says. Rapid diagnostic tests (RDTs) offer a promising alternative for several diseases, including malaria, syphilis, and adult HIV. These antigen- or antibody-based diagnostics are not lab or electricity dependent and can provide results within 15 to 20 minutes. Community health workers can use them with minimal formal training. 

However, Harvey says, RDTs are often much more expensive that laboratory-based alternatives. In addition, while RDTs do not demand a high level of technical skill, some training is required.  Since most use whole blood, community-based RDTs raise biosecurity concerns. Transport from manufacturer to end user can take as long as 12-18 months, a good part of the 24-month shelf life.

A few simple steps to test accuracy and practicality

Test developers, Harvey says, can take a few relatively simple steps towards improving test accuracy and practicality:

• Self contained packaging: The end-user often will not have access the supplies they need to perform the tests. Tests will be used more effectively and safely if a package includes all necessary supplies.
• Testing of specimen collection devices: End users often find it difficult to manipulate blood collection devices. Tests which involve actual end users under real-world conditions can iron out problems before a product is brought to market. In addition, Harvey says, using illustrations rather than words in the manufacturer’s instructions can significantly increase performance.

For more information or a copy of the article, please contact Steven Harvey at sharvey@urc-chs.com.

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