Effectiveness of vitamin D2 compared with vitamin D3 replacement therapy in a primary healthcare setting: a retrospective cohort study

Introduction: Vitamin D deficiency is a worldwide public health concern, which can lead to severe diseases, such as rickets in children and osteomalacia in adults. Most studies have compared equimolar unit-to-unit doses of vitamin D2 and D3. Objectives: The current study aimed to answer the research question: “How effective is vitamin D2 (600,000 U/1.5 ml) compared to vitamin D3 (300,000 U/1 ml) parenteral supplementation for raising serum vitamin D levels in adult patients treated in a primary health care setting?” Setting: Primary Health Care Corporation (PHCC) runs 28 health centers distributed throughout the State of Qatar and its capital city, Doha. Qatar is on the east coast of the Arabic peninsula, with very hot and sunny summers and a desert climate. Study design: This was a retrospective observational cohort study. Method: A total of 15,716 participants were recruited following ethical approval. They were identified by electronic medical records (EMR) describing the clinical encounters of individuals aged 18 to 60-years-old who attended a health center operated by the PHCC during the 3.5-year study period from January 1, 2017 to June 30, 2020. The PHCC EMR system uses SNOMED codes (a systematically organized computer-processable collection of medical terms providing codes, names, synonyms, and definitions implemented for clinical documentation and reporting). Four study groups were created depending on the type of vitamin D injection and the oral form of replacement therapy. The analysis scheme used the serum vitamin D level within the preceding 4 weeks (pretreatment), followed by administration of the treatment dose. The post-treatment serum testing value should have been available within a maximum of 12 weeks. The Statistical Package for Social Sciences (IBMSPSS; IBM Corp., Armonk, NY, USA) version 23 software was used for the statistical analysis. Results: Four treatment options were compared, including a vitamin D2 injection, a vitamin D3 injection, combined use of a vitamin D2 injection + a D2 tablet, and combined use of a vitamin D3 injection + a D2 tablet. All four treatment groups were associated with a statistically significant increase in serum vitamin D within a maximum of 12 weeks of follow-up. The vitamin D2 injection alone was associated with the lowest increase in serum concentration by a mean of 3.2 ng/ml. In contrast, the vitamin D3 injection alone or with a D2 tablet increased serum vitamin D by 6.1 and 5.6 ng/ml, respectively. Using the combination of a vitamin D2 injection and a tablet only added a marginal increase of 2.3 ng/ml in serum vitamin D on top of the 3.2 ng/ml increase attained after administering the D2 injection alone. Conclusion: Utilizing vitamin D3 in an injectable form is the best choice to restore severe vitamin D deficiency. Furthermore, it was superior to the injectable form of vitamin D2, even though vitamin D2 has double the molar units.