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 |