Diagnostic Assays Evaluated for Vitamin B12 and Folate Deficiency

Current guidelines pertaining to diagnosing macrocytic anemia in association with vitamin B12 and folate deficiency recommend that vitamin B12, folate, homocysteine, and methylmalonic acid assays should be assessed concurrently due to their close relationship in metabolism.

Folate is essential for the prevention of a wide spectrum of health issues, including, most notably, megaloblastic anemia and neural tube defects. Vitamin B12 is a cofactor of methionine synthase and L‐methylmalonyl–coenzyme A mutase, and the interaction between folate and vitamin B12 is responsible for the megaloblastic anemia seen in both vitamin deficiencies.

Medical Laboratorians at the Green Cross Laboratories (Yongin, Republic of Korea) retrospectively reviewed the test results from Korean adults who underwent hemoglobin (Hb) testing between September 25, 2017, and June 30, 2019, through the laboratory information system. The laboratory provides clinical specimen analysis services including serum folate, erythrocyte folate, serum homocysteine, and methylmalonic acid (i.e., serum, plasma, random urine, and 24‐hour collected urine) tests; complete blood count findings including Hb; and erythrocyte mean corpuscular volume (MCV) to clinics and hospitals nationwide.

Hb and MCV were analyzed using Sysmex XN 9000 analyzers (Sysmex Corporation, Kobe, Japan). Serum and erythrocyte folate were determined using the Elecsys Folate assay on Cobas 8000 e801 analyzers (Roche Diagnostics, Mannheim, Germany). Serum homocysteine level was determined using the AutoLab Homocysteine assay (IVD‐LAB, Uiwang-si, South Korea) on Roche Diagnostics’ Cobas 8000 c702 analyzers. Methylmalonic acid concentration in serum, plasma, random urine, and 24‐hour collected urine samples were measured using a Clarus 680 gas chromatography‐mass spectrometry analyzers (PerkinElmer, Waltham, MA, USA).

The scientists reported that during the study period, 109,524 Korean adults completed Hb tests. Among them, 14,894 (13.6%) received concurrent erythrocyte MCV tests. Among these 14,894 adults, 265 adults (107 men and 158 women; 1.2%) aged 23.9 to 95.4 years (median: 68.8 years) had macrocytic anemia, showing Hb findings below the lower limit of the reference interval for each sex and gender and MCV results of greater than 102 fL, from among 94 local clinics or hospitals without in‐house clinical laboratories. Among 265 patients with macrocytic anemia, only one woman underwent both serum vitamin B12 (464 pg/mL, reference interval: 197‐771 pg/mL) and folate (3 ng/mL, reference interval: 3.9‐26.8 ng/mL) assays. Separately, one man from a different clinic underwent serum homocysteine testing during the study period (12.0 µmol/L; upper reference limit: 15.4 µmol/L) and his results were within the reference interval.

The authors concluded that their study provided basic information regarding utilization rates of assays in association with vitamin B12 and folate deficiency. Making more data available is expected to improve rates of testing in patients with macrocytic anemia in local clinics and hospitals without in‐house clinical laboratories in Korea. The study was published on November 6, 2020 in the Journal of Clinical Laboratory Analysis.

Related Links:
Green Cross Laboratories
Sysmex Corporation
Roche Diagnostics
IVD‐LAB
PerkinElmer