Table 1.
Product features of a point-of-care G6PD test in support of radical cure
| Features | Ideal | Acceptable | Comments |
|---|---|---|---|
| Test output |
Binary, deficient/normal |
Quantitative |
Presumes a consensus definition of normal that aligns with drug safety |
| User |
Village health workers, mobile malaria workers |
District hospital, laboratory worker |
This will be defined by national malaria control programmes |
| Platform |
Point-of-care similar to a malaria rapid diagnostic test |
A disposable device coupled to a portable, battery-operated device; sensitivity significantly better than human eye |
A reader would be acceptable if it significantly improves operational performance |
| Specimen type |
Capillary blood |
Capillary blood |
Tests must be evaluated for performance with this specimen type |
| Stability requirements |
2 years at 37°C |
1 year at 37°C |
Expect low throughput at clinic level, so requires small quantities per package or long shelf life |
| Packaging |
Maximum 25 tests per kit |
Maximum 25 tests per kit |
|
| Operational temperature range |
25-40°C |
25-40°C |
G6PD enzyme activity is highly temperature dependent (see Figure 2) |
| Operational humidity range |
40-90% |
40-90% |
None. |
| Time to result |
<10 minutes |
<30minutes |
Availability of the test result should be aligned with malaria diagnosis and treatment work flow |
| Read window |
>1 hour |
10 minutes |
Ideally, the test result can be read at any time point after the initial time to result |
| Sensitivity |
Detects all patients (100%) with G6PD activity less than a predetermined cut-off, at or less than which it is unsafe to prescribe a particular dosage of an 8-aminoquinoline |
>95% for patients at or less than a defined cut-off G6PD activity |
For primaquine, where the fluorescent spot test has been accepted as the standard of care, a 30-40% normal G6PD activity cut-off should be used; for new drugs such as tafenoquine, the cut-off is likely to be higher |
| Specificity |
>95% |
>70% |
It is preferable to have some patients with normal G6PD activity levels classified as deficient as determined by the Receiver Operating Curve of a diagnostic test |
| Price | Similar to or less than a malaria rapid diagnostic test | Similar to or less than a malaria rapid diagnostic test | G6PD test represents an additional cost over that of malaria diagnosis and treatment |