used proactively. This chapter summarizes the workshop presentations and discussions addressing the need for rapid diagnostics, progress on point-of-care diagnostics, the challenges of laboratory capacity in South Africa, and the use of biomarkers to diagnose TB.

NEED FOR RAPID DIAGNOSTICS1

Although some have suggested that greater than 70 percent detection and cure rates for TB will constitute success, van Helden suggested that in fact, this will not be enough. If only 70 percent of infected individuals are detected and only 70 percent of that group is cured, the overall cure rate will be the product of those two numbers, or 49 percent. Furthermore, even infected people whose disease resolves will spread the organism before they are diagnosed. A mathematical model suggests that if diagnosis takes 40 days, a rising epidemic will continue, whereas diagnosis within 6 days or less will result in the epidemic’s decreasing.

The need for patients to return to the clinic is a factor. Studies of the current system for diagnosis indicate that 20 percent of patients fail to return after their first visit to a clinic and thus are lost to follow-up. A point-of-care diagnostic device (see the discussion below) could prevent those patients from being lost to follow-up at that early stage of diagnosis and treatment of their TB. The algorithm used suggests that typically when patients present to a clinic or TB facility, a point-of-care test that may be 40–50 percent sensitive is administered. Positive patients are absorbed into therapy, and it may not be necessary that they provide another sputum sample. Negative patients that are highly clinically suspicious should be managed according to the normal National Health Laboratory Service algorithm for that country, suggested van Helden.

Considerations and Trade-Offs in Developing and Adopting Diagnostics

In considering what types of diagnostic tests should be developed and adopted within a high-burden country, a number of criteria come into play. An ideal needs assessment may have to be evaluated and judged against what is realistic.

To illustrate this point, van Helden used the example of the Ziehl-Neelsen stain test,2 which is used to evaluate sputum. Many argue that this test is appropriate because it is effective, relatively quick, and inexpensive. Others argue that it is insufficient, and a test that is better on all criteria

1

This section is based on the presentation of Paul van Helden, Stellenbosch University.

2

The Ziehl-Neelsen stain, also known as the acid-fast stain, is a special bacteriological stain used to identify acid-fast organisms, mainly mycobacteria.



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