Clinical perspectives on hemoglobin measurement: The example of malaria radical cure

Hemoglobin (Hb) testing is widely used to inform clinical care and assess population health. A World Health Organization (WHO)-UNICEF expert group recently recommended use of venous blood tested using an automated hematology analyzer as best practice for Hb measurement in population surveys. Recently updated WHO guidelines recommend the same methods for both populations and individuals. However, in low-resource settings where these methods are often inaccessible, the performance and clinical utility of simpler methods, defined by their accuracy for key clinical decisions and impact on patient management, should be considered. We discuss Hb test performance requirements for clinical contexts as opposed to population surveys, and consider acceptability criteria specific to a test's context and intended use. Using the example of malaria case management and radical cure, we consider the clinical risk/benefit of the incidental Hb measurement provided on a point-of-care (POC) test for glucose-6-phosphate dehydrogenase (G6PD) deficiency (the STANDARD G6PD Test), which is required to inform optimal malaria radical cure. We review evidence from clinical evaluations, where Hb was measured in venous and capillary blood using the HemoCue 201+ and the STANDARD G6PD Test, and compared to venous Hb results from an automated hematology analyzer. If Hb was not measured, radical cure could be incorrectly prescribed or withheld in more individuals with severe anemia, relative to treatment errors that could be made if any POC Hb test method were used. Overall agreement with the gold-standard Hb measure varied from 98.4% to 99.5% for identifying severe anemia. In the absence of Hb POC testing, diagnosing anemia based on clinical signs is unlikely to improve these results. We highlight the importance of evaluating the acceptable performance of POC tests by considering clinical risks/benefits specific to the intended use and health system context to improve case management where alternate solutions are unavailable or unaffordable.