Investigations
1st investigations to order
FBC and peripheral blood smear
Test
To look for other haematological disorders mimicking scurvy.
Result
normocytic anaemia (expected); microcytic or megaloblastic anaemia if other nutritional deficiencies are present
serum ascorbic acid
Test
Ordered during initial evaluation to help to identify the amount and severity of vitamin C deficiency and to exclude haematological disorders mimicking scurvy.[1][64] Sensitivity and specificity are high.
Scurvy has not been reported in patients with adequate levels of vitamin C, except in people previously on high daily doses of vitamin C with rapid decline in daily dose.[26] Alternative diagnoses should be strongly considered.[1]
Result
deficient level (high risk): <11.4 micromol/L (<0.2 mg/100 mL); low level (medium risk): 11.4-16.5 micromol/L (0.2-0.29 mg/100 mL); acceptable level (low risk): >17 micromol/L (>0.3 mg/100 mL)
leukocyte ascorbic acid
Test
Ordered during initial evaluation to help to identify the amount and severity of vitamin C deficiency and to exclude haematological disorders mimicking scurvy.[1][64] Sensitivity and specificity are high.
Scurvy has not been reported in patients with adequate levels of vitamin C, except in people previously on high daily doses of vitamin C with rapid decline in daily dose.[26] Alternative diagnoses should be strongly considered.[1]
Result
deficient level (high risk): <57 nanomol/10^8 cells; low level (medium risk): 57-114 nanomol/10^8 cells; acceptable level (low risk): >114 nanomol/10^8 cells
whole blood ascorbic acid
Test
Ordered during initial evaluation to help to identify the amount and severity of vitamin C deficiency and to exclude haematological disorders mimicking scurvy.[1][64] Sensitivity and specificity are high.
Scurvy has not been reported in patients with adequate levels of vitamin C, except in people previously on high daily doses of vitamin C with rapid decline in daily dose.[26] Alternative diagnosis should be strongly considered.[1]
Result
deficient level (high risk): <11 micromol/L (<0.2 mg/100 mL); low level (medium risk): 11-27 micromol/L (0.2-0.47 mg/100 mL); acceptable level (low risk): >23 micromol/L (>0.4 mg/100 mL)
x-ray of knee and wrist
Test
Ordered during initial evaluation to exclude disorders mimicking scurvy. Sensitivity and specificity are high for some signs, as described.[1][65]
Pelkan's sign shows irregularities, fragmentation, and spurs at the metaphyseal margins.
Frankel's sign is a lucent line (Trummerfeld zone or scurvy line) immediately beneath a white line at the margin of the growth plate. This sign is thought to be highly specific.
Result
corner fraction sign, a ground-glass appearance, trabecular atrophy, Pelkan's sign, Frankel's sign
Investigations to consider
MRI of knee, wrists, and long bones in paediatric cases
Test
Other tests are probably of greater diagnostic yield. The MRI features may be a coincidental finding when other diagnoses are being pursued, including work-up for pseudo-paralysis.[66][67]
Result
T1-weighted images: bone marrow unremarkable or heterogeneous high and low signal intensities; subperiosteal fluid collection with low signal intensity; T2-weighted images: bone marrow with heterogeneous high and intermediate signal intensity; periosteum may have high signal intensity
bone marrow biopsy
Test
Should be ordered if scurvy diagnosis is in question, or if the patient's illness is rapidly progressing during initial treatment. Given relatively rapid response to vitamin C, this invasive test may be delayed in most cases where scurvy is strongly suspected.
Result
normal or erythroid hyperplasia
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