Test utilization for the diagnosis of vitamin B12 and folate deficiency in local clinics in Korea

Abstract Background 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. We aimed to investigate the completion of these assays in local clinics and hospitals without in‐house clinical laboratories in Korea. Methods We retrospectively reviewed data from the laboratory information system between September 25, 2017, and June 30, 2019, to investigate usage rates of vitamin B12, folate, homocysteine, and methylmalonic acid assays in patients with macrocytic anemia. Results During the study period, 14 894 Korean adults among 109 524 (13.6%) total hemoglobin‐tested subjects underwent concurrent erythrocyte mean corpuscular volume (MCV) tests. Among these 14,894 adults, 265 (1.2%) from 94 local clinics or hospitals without in‐house clinical laboratories in Korea had macrocytic anemia. Furthermore, among these 265 adults, only one woman underwent serum vitamin B12 and folate assay and one man underwent serum homocysteine testing during the study period. No patients among the 265 individuals with macrocytic anemia received erythrocyte folate or methylmalonic acid testing (with either serum, plasma, random urine, or 24‐hour collected urine). Conclusions The results of this study provide 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.


| INTRODUC TI ON
Folate is essential for the prevention of a wide spectrum of health issues, including, most notably, megaloblastic anemia and neural tube defects. 1 Neural tube defects are major birth defects of the brain and spine that occur early in pregnancy due to improper closure of the embryonic neural tube, which may lead to a range of disabilities or death of the infant. 2 Vitamin B12 is a cofactor of methionine synthase and L-methylmalonylcoenzyme A mutase, and the interaction between folate and vitamin B12 is responsible for the megaloblastic anemia seen in both vitamin deficiencies. 3 Vitamin B12 is also necessary for the development and initial myelination of the central nervous system as well as for the maintenance of its normal function; thus, vitamin B12 deficiency has been known to causes megaloblastic anemia, demyelinating neurologic disease, or both. 3 Current guidelines for diagnosing vitamin B12 and folate deficiency recommend that vitamin B12 and folate assays should be conducted concurrently due to the close relationship in metabolism. 4 However, although often used as the first-line screening test for vitamin B12 or folate deficiency, serum vitamin B12 or folate in serum and/or in erythrocyte measurement used in isolation show generally poor sensitivities and specificities for the reliable detection of vitamin B12 or folate deficiency. 5 Since 5-methyltetrahydrofolate, the main form of folate found in blood, is essential for the vitamin B12-dependent methionine synthase-mediated remethylation of homocysteine to methionine, the measurement of methylmalonic acid, homocysteine, or both is used to confirm vitamin B12 deficiency in untreated patients; thus, an elevated level of methylmalonic acid is more sensitive and specific for the diagnosis. 1,3 Test utilization necessitates not only reducing costs by eliminating unnecessary testing but also selecting the most appropriate tests to drive value and improve patient outcomes. 6,7 Test "underutilization" occurs when a provider does not request a test that could positively affect patient outcomes, which may lead to an incorrect or delayed diagnosis. 6,8 To improve the quality of clinical laboratories, improving the assessment and understanding of the current status of testing are essential for establishing meaningful metrics and monitoring the effectiveness of a particular action implemented to alter said rates of utilization. 6,9 However, to the best of our knowledge, only limited data suggesting the conduct of vitamin B12, folate, homocysteine, and methylmalonic acid assays to diagnose and manage patients with macrocytic anemia in association with vitamin B12 and folate deficiency in Korean adults exist at this time.
Thus, in this study, we investigated the completion rates of vitamin B12, folate, homocysteine, and methylmalonic acid assays for diagnosing and managing Korean adult patients with macrocytic anemia in association with vitamin B12 and folate deficiency who visited local clinics and hospitals without their own clinical laboratories for the first time in Korea.

| MATERIAL S AND ME THODS
We 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 of Green Cross Laboratories. Green Cross Laboratories, one of the largest referral clinical laboratories in South Korea, provides clinical specimen analysis services including serum folate, erythrocyte folate, serum homocysteine, and methylmalonic acid (ie, 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. Missing data for age or sex were excluded. All data were anonymized before being adopted for statistical analysis. The protocol of this study was approved by the institutional review board (IRB) of Green Cross Laboratories (IRB GCL-2020-1014-01). A waiver of informed consent was approved by the IRB since the use of a waiver would not adversely affect the rights or welfare of the study subjects because the study was retrospective and involved no more than minimal risk to the subjects. The study was conducted in accordance with the Mann-Whitney U test when appropriate was adopted to compare age in sex groups. All P-values of less than 0.05 were considered to be significant. Statistical analyses were executed using Microsoft

| D ISCUSS I ON
In this study, we investigated the adoption of vitamin B12, folate, homocysteine, and methylmalonic acid assays in association with vitamin B12 and folate deficiency in adult patients with macrocytic anemia in local clinics and hospitals without in-house clinical laboratories in South Korea. To the best of our knowledge, this is the first study to focus on the rates of vitamin B12, folate, homocysteine, and methylmalonic acid assays performed in patients with macrocytic anemia visiting local clinics and hospitals.
In this study, the adoption of serum vitamin B12 and folate and serum homocysteine assays was below 0.5% among all patients with macrocytic anemia (1/295) and 1.1% (1/94 clinic each) for total clinics and hospitals while those rates of erythrocyte folate and methylmalonic acid tests in varied specimen types were 0.0%.
During the study period, methylmalonic acid assays using varied specimen types were conducted by university and hospitals with own clinical laboratories. Although the scope of this study was to examine test utilization in local clinics without their own clinical laboratories, during the study period, 259 patients were tested for methylmalonic acid using 24-hour urine and 13 of them presented

Thanks to Ms Hyunjoo Son and Ms Jiseon Kim at Green Cross
Laboratories for their support and document management.

CO N FLI C T S O F I NTE R E S T
The authors declare no conflict of interest.

AUTH O R CO NTR I B UTI O N S
All authors contributed to article preparation. Rihwa Choi contrib-

DATA AVA I L A B I L I T Y S TAT E M E N T
The datasets generated and analyzed during the current study are available from the corresponding authors on reasonable request.