Comparison of two methods for measuring 25-OH vitamin D in the follow-up of patients after bilio-pancreatic diversion bariatric surgery.

OBJECTIVE: Our objective was to compare the ECLIA from Roche versus the LC-MS/MS method for quantitation of serum 25-hydroxy-vitamin D in patients who have undergone bariatric surgery.

DESIGN AND METHODS: Cross-sectional and correlational studies were performed on three different groups for the 25-OH-D levels quantitated by both methods. The control group of apparently healthy subjects was randomly selected in a clinical chemistry laboratory. Test groups were patients who had undergone bilio-pancreatic diversion (BPD) and were supplemented either with vitamin D2 or with vitamin D3. The number of samples per group was established according to the CLSI recommendation protocol (EPO9-A2-IR).

RESULTS: The agreement of LC-MS/MS with the Roche method was acceptable in the apparently healthy subjects group and in the post-BPD D3-supplemented group with an average bias of -1.7% and -9.2%, respectively. However, this agreement was unacceptable in the post-BPD D2-supplemented group with an average bias of -45.3%. The LC-MS/MS enabled us to detect four patients who had excess vitamin D or poisoning with vitamin D for which it was necessary to stop the supplementation with vitamin D in the D2 -supplemented group.

CONCLUSION: Despite the apparent good agreement between the Roche method and LC-MS/MS in the healthy subjects group and in the post-DBP D3-supplemented patient group, a considerable bias seems to exist, particularly in the presence of D2. The LC-MS/MS method is therefore the most accurate method to follow the vitamin D2 -supplemented bariatric population.