Table 2.
Logistic regression analyses for interaction between the baseline characteristics and treatment at 3, 12, and 24 months
| Baseline characteristic | 3 months (< MIC 139 vs. ≥ MIC 174)a |
12 months (< MIC 80 vs. ≥ MIC 199)a |
24 months (< MIC 71 vs. ≥ MIC 218)a |
|||
|---|---|---|---|---|---|---|
| Marker-by-treatment interaction | Marker-by-treatment interaction | Marker-by-treatment interaction | ||||
| ORb (95% CI) |
p value for interaction | ORb (95% CI) |
p value for interaction | ORb (95% CI) |
p value for interaction | |
| Age | 0.95 (0.89–1.02) | n.s. (0.14) | 0.93 (0.84–1.00) | 0.06* | 0.92 (0.84–0.10) | 0.05* |
| Education level (1–7) | 1.02 (0.41–2.50) | n.s. (0.97) | 0.65 (0.22–1.90) | n.s. (0.43) | 1.01 (0.34–3.02) | n.s. (0.98) |
| BMI | 0.93 (0.83–1.05) | n.s. (0.24) | 0.86 (0.75–0.10) | 0.05* | 0.94 (0.82–1.09) | n.s. (0.41) |
| Knee function on the IKDC (0–100) | 1.04 (0.10–1.07) | 0.07* | 1.01 (0.97–1.05) | n.s. (0.52)0 | 1.03 (0.99–1.08) | n.s. (0.16) |
| General physical health on RAND-36 PSC (0–100) | 1.08 (1.02–1.15) | 0.01* | 1.05 (0.99–1.12) | n.s. (0.11) | 1.04 (0.97–1.11) | n.s. (0.30) |
| Pain intensity during activities on VAS (0–100) | 0.97 (0.95–0.10) | 0.02* | 0.99 (0.96–1.01) | n.s. (0.25) | 0.10 (0.97–1.02) | n.s. (0.79) |
| Expectation of pain relief (1–7) | 1.31 (0.63–2.71) | n.s. (0.47) | 0.88 (0.38–2.06) | n.s. (0.77) | 1.62 (0.65–4.07) | n.s. (0.30) |
| Knee osteoarthritis on K–L scale (0–4)c | 0.71 (0.27–1.85) | n.s. (0.48) | 0.99 (0.32–3.11) | n.s. (0.99) | 1.22 (0.39–3.87) | n.s. (0.74) |
Abbreviations: MIC minimally important change, OR odds ratio, CI confidence intervals, IKDC International Knee Documentation Committee Subjective Knee, RAND-36 PCS Physical Component Scale for or general physical health, BMI body mass index, K–L Kellgren–Lawrence scale
Marker-by-treatment interactions per follow-up moment are shown
a(n = < MIC vs. n = ≥ MIC) For each follow-up moment the distribution of patients who experienced MIC in knee function (improvement ≥ 11 IKDC points) and patients who did not experience a MIC in knee function (changed IKDC score < 11 points) is reported. The reference treatment is physical therapy. Data were available of 313 patients at 3 months, 279 patients at 12 months, and 289 patients at 24 months
bFor each marker-by-treatment interaction, the OR shows the relative change per unit increase in the marker and we reported the 95% CI of the OR. An OR ≥ 1 indicates the value is in favour of physical therapy. The p values expressed whether the marker-by-treatment interaction is significant (p ≤ 0.1)
cWe analysed educational level, expectation of pain relief an K–L score as a continuous variable in the logistic regression analyses
*Indicates the baseline characteristics that are potential treatment selection markers