Investigations
1st investigations to order
FBC
Test
First test to perform. FBC shows anaemia (haemoglobin 40 to 100 g/L [4 to 10 g/dL], depending on severity), which is typically normochromic and normocytic/mildly macrocytic, with an increased MCHC.
Result
anaemia and normochromic red cell index
reticulocyte count
Test
Indicates marrow response to anaemia.
Result
reticulocyte percentage typically elevated to >0.10 (>10%) (degree of elevation proportional to the degree of anaemia)
urinalysis
Test
Dipstick testing detects urobilinogen and protein if intravascular haemolysis is present.
Result
haemoglobinuria
unconjugated (indirect) bilirubin
Test
Increased haem catabolism.
Result
elevated
lactate dehydrogenase (LDH)
Test
Elevated LDH as a consequence of RBC destruction and haemoglobin release.
Result
high
haptoglobin
Test
Binds free haemoglobin; low plasma values suggest intravascular haemolysis.
Result
low
peripheral blood smear
Test
Presence of blister or bite cells suggests oxidative stress as a cause of haemolysis. Heinz bodies (fragments of denatured haemoglobin) are seen in acute haemolysis.
Result
anisocytosis, abnormal forms, bite cells
Investigations 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.[26][33][34]
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.[26][33][34]
Result
reduced G6PD activity
molecular analysis
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 programmes or to determine the safety of primaquine treatment in the context of Plasmodium vivax malaria control programmes), but availability may be limited.[40]
Result
negative
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