Assessment of vitamin D levels in newly diagnosed children with type 1 diabetes mellitus comparing two methods of measurement: a facility’s experience in the Middle Eastern country of Bahrain

BACKGROUND: The number of children being diagnosed with type 1 diabetes mellitus (T1DM) is on the rise and has more than doubled in the past 10 years in Bahrain. Some studies have linked low vitamin D levels with an increased risk of diabetes. There are concerns regarding the variations in circulating 25(OH)D levels measured by different laboratories and by using different analytical techniques. OBJECTIVE: The aim of this study was to evaluate the vitamin D levels of newly diagnosed children with T1DM using the “gold standard method” with high-pressure liquid chromatography–tandem mass spectrometry methods compared to the chemiluminescence micro-particle immunoassay (CMIA) used in a hospital laboratory. SUBJECTS: Eighteen children, aged 6–12 years, who received a confirmed diagnosis of T1DM in 2014 were chosen as subjects. METHODS: Serum vitamin D levels were assessed in a hospital, while an extra aliquot of blood collected during routine blood collection after acquiring informed written consents from the subjects, and sent to Princess Al-Jawhara Center for Molecular Medicine and Inherited Disorders to be analyzed by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS). RESULTS: The mean age of the study group was 9±2 years. The mean total of 25(OH)D levels (D(3) and D(2)) assessed by UPLC-MS/MS was 49.7±18.8, whereas the mean total of 25(OH)D levels obtained from the CMIA assay was 44.60±13.20. The difference in classification between the two methods was found to be statistically significant (P=0.004). A Bland–Altman plot showed a poor level of agreement between the two assay methods. The CMIA overestimated insufficient values and underestimated deficiency, when compared to UPLC-MS/MS. CONCLUSION: There was a statistically significant difference between the two assay methods with CMIA overestimating vitamin D insufficiency. Clinicians should be prudent in their assessment of a single vitamin D reading, when the gold standard method is not available or feasible.