Change in serum 25(OHD) and iPTH concentration at 6-month and 24-month follow-up by treatment
| Standard-dose800 IU vitamin D3 (n=136) | High-dose2000 IU vitamin D3 (n=137) | P value* difference by time point | P value† difference over time | |
| 25(OH)D (ng/mL) | ||||
| Baseline | 26.8 (24.9 to 28.7) | 27.7 (25.8 to 29.6) | 0.51 | <0.0001 |
| 6 months | 40.4 (38.4 to 42.3) | 47.0 (45.1 to 49.0) | <0.0001 | |
| 24 months | 37.1 (35.1 to 39.2) | 45.5 (43.5 to 47.6) | <0.0001 | |
| Pover time‡ | <0.0001 | <0.0001 | ||
| iPTH (ng/L) | ||||
| Baseline | 49.8 (46.8 to 52.9) | 48.7 (45.7 to 51.7) | 0.62 | 0.22 |
| 6 months | 50.5 (47.4 to 53.5) | 47.8 (44.8 to 50.9) | 0.22 | |
| 12 months | 52.7 (49.6 to 55.8) | 48.5 (45.4 to 51.6) | 0.06 | |
| 18 months | 53.5 (50.4 to 56.6) | 49.5 (46.4 to 52.6) | 0.07 | |
| 24 months | 52.4 (49.3 to 55.6) | 48.8 (45.7 to 52.0) | 0.11 | |
| Pover time‡ | 0.004 | 0.59 |
Data show LSM (95% CI) of repeated measurements of serum 25-OH(D) and iPTH concentration by treatment group from multivariable repeated-measures models. Models included an indicator variable for treatment, visit, and the interaction between treatment and visit, and were adjusted for preoperative Western Ontario and McMaster Universities Arthritis Index.
Function score (<52 vs ≥52 in the operated knee), presence of osteoarthritis in the non-operated knee, hospital site, and baseline age, gender, body mass index and Charlson Comorbidity Index (score 0–37). P values are two-sided. Statistical significance was set at p<0.05.
*P value for the difference in 25(OH)D and iPTH concentration by treatment group at baseline and individual follow-up time points.
†P value for the overall treatment effect across the repeated measurements of 25(OH)D and iPTH concentration.
‡P value for the change in 25(OH)D and iPTH concentration within treatment groups over time.
25(OH)D, 25-hydroxyvitamin D; iPTH; intact parathyroid hormone; LSM, least-square means.