Tests
1st tests to order
CBC
Test
First test to perform. CBC shows anemia (Hb 4-10 g/dL, depending on severity), which is typically normochromic and normocytic/mildly macrocytic, with an increased MCHC.
Result
anemia and normochromic red cell index
reticulocyte count
Test
Indicates marrow response to anemia.
Result
reticulocyte percentage typically elevated to >0.10 (>10%) (degree of elevation proportional to the degree of anemia)
urinalysis
Test
Dipstick testing detects urobilinogen and protein if intravascular hemolysis is present.
Result
hemoglobinuria
unconjugated (indirect) bilirubin
Test
Increased heme catabolism.
Result
elevated
LDH
Test
Elevated LDH as a consequence of RBC destruction and hemoglobin release.
Result
high
haptoglobin
Test
Binds free hemoglobin; low plasma values suggest intravascular hemolysis.
Result
low
peripheral blood smear
Test
Presence of blister or bite cells suggests oxidative stress as a cause of hemolysis. Heinz bodies (fragments of denatured Hb) are seen in acute hemolysis.
Result
anisocytosis, abnormal forms, bite cells
Tests to consider
G6PD fluorescent spot test
Test
Detects deficient production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) from nicotinamide adenine dinucleotide phosphate (NADP).
NADPH is fluorescent and its absence (due to G6PD deficiency) results in lack of fluorescence.
Result
negative
G6PD spectrophotometry
Test
Spectrophotometric analysis of NADPH production from NADP quantifies enzyme activity. Quantitative spectrophotometric assay should be undertaken to confirm or exclude diagnosis if the screening test is abnormal or borderline.[25][30][31]
G6PD activity should be measured by quantitative spectrophotometric assay first line in female patients. A cytochemical test should be undertaken if quantitative assay results are intermediate or equivocal or if there is a clinical or genetic reason to suspect that a woman is heterozygous for G6PD deficiency.[25][30][31]
Result
reduced G6PD activity
molecular analysis
Test
Can be considered when initial tests are equivocal. Candidates for molecular analysis include heterozygous females, and males with Klinefelter syndrome (who may have intermediate G6PD activity).[25]
G6PD variants can be ascertained using polymerase chain reaction (PCR).[33][34][35] If there are existing genetic test results, do not perform repeat testing unless there is uncertainty about the existing result, e.g., the result is inconsistent with the patient’s clinical presentation or the test methodology has changed.[36]
Result
positive
Emerging tests
point of care testing
Test
Rapid diagnostic testing can be useful in certain situations at the point of care (e.g., neonatal screening programs or to determine the safety of primaquine treatment in the context of Plasmodium vivax malaria control programs), but availability may be limited.[32]
Result
negative
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