Scoping review of micronutrient imbalances, clinical manifestations, and interventions

Table 1 Laboratory testing for diagnostic evaluation of several micronutrient deficiencies

Vitamin	Diagnostic test	Specimen type	Diagnostic values
A	Vitamin A (retinol) level	Serum	Low
D	Total 25-hydroxyvitamin D level	Serum	Low
E	Vitamin E (α-tocopherol) level	Serum	Low
K1	PT/INR	Serum	Prolonged/elevated
Thiamine2	Thiamine, whole blood	Whole blood EDTA	Low
Riboflavin	Riboflavin level or urinary excretion rate	Plasma or urine	Low
Niacin	Niacin level or urinary excretion of N1-methylnicotinamide	Serum or urine	Low
Pantothenic acid	Pantothenic acid level	Serum	Low
Pyridoxine3	Pyridoxal phosphate	Serum	Low
Biotin	Biotin level	Serum	Low
Folate	Vitamin B12 and folate levels	Serum	Low
Cobalamin4	Vitamin B12 and folate levels	Serum	Low
Ascorbic acid5	Ascorbic acid level	Serum	Low

¹If phytonadione (Vitamin K1) 1 mg IV dramatically decreases PT within 2-6 hours, a liver disorder is unlikely, and the diagnosis of vitamin K deficiency is confirmed.

²This assay measures the concentration of the primary active form of vitamin B1 (thiamine diphosphate). Approximately 90 percent of B₁ present in whole blood is thiamine diphosphate. Thiamine monophosphate and thiamine, which comprise the remaining 10 percent, are not measured. Values less than 70-180 nmol/L are considered diagnostic for thiamine deficiency. The United States Food and Drug Administration has not cleared or approved it. The thiamine loading test, which measures erythrocyte transketolase in red blood cells, is still the best indicator for thiamine deficiency. However, the test is expensive and time-consuming.

³Diagnosis of pyridoxine deficiency is usually made clinically. There is no single acceptable laboratory testing to confirm diagnosis. However, serum pyridoxal phosphate is usually the most common.

⁴A complete blood count, in conjunction with B12 and folate levels, should be obtained to detect megaloblastic anemia. Folate levels should also be measured to differentiate B12 from folate deficiency as a cause of anemia, as folate supplementation may alleviate megaloblastic anemia but worsen neurologic deficits.

⁵Vitamin C deficiency is a clinical diagnosis based on risk factors and gingival or skin findings. Laboratory diagnosis requires the measurement of blood ascorbic values. < 0.2 mg/dL (< 11 mcmol/L) indicate vitamin C deficiency.

PT: Prothrombin time; INR: International normalized ratio; EDTA: Ethylenediaminetetraacetic acid.