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Table 3 Predictors for being in the best tertile of GHP scores

From: Subcutaneous immunoglobulin in primary immunodeficiency – impact of training and infusion characteristics on patient-reported outcomes

Predictor Category Logistic regression Linear regression
OR 95% CI p-value Coefficient 95% CI p-value
Age 0–17 years 1   0.006 0   0.004
≥18 years 0.30 0.12, 0.70 −0.52 −0.88, −0.16
Experience with IgG prior to SCIG Ig-naïve 1   0.01    
Ig-experienced 2.36 1.22, 4.54
Time on treatment < 2 years     0   0.06
≥2 years 0.27 −0.01, −0.54
Confidence after traininga 1–5 1   0.03    
6–7 2.18 1.07, 4.44
Number of sites 1–3 1   0.01 0   0.04
≥4 0.44 0.24, 0.84 −0.24 −0.47, −0.02
TSQM effectiveness scoreb T2 + T3, ≤75 1   0.001 0.13 0.07, 0.18 < 0.001
T1, ≥76 (best) 2.73 1.50, 4.80
PROMIS Fatiguec T2 + T3, ≥54 1   < 0.001 −0.33 −0.39, −0.26 < 0.001
T1, ≤53 (best) 8.26 4.56, 15.0
  1. Multivariate logistic regression and linear regression models calculated predictors for being in the best tertile of GHP scores. GHP was measured on an anchored numeric 1–7 scale (1 = poor health and 7 = excellent health), where respondents were grouped in T2 + T3 (intermediate/worst) if they had a score of ≤ 5 and in T1 (best) if they scored 6 or 7. PROMIS Fatigue T-scores are obtained from published raw score to T-score concordance tables of the PROMIS Fatigue Short Form 7a. With 5 levels on each of the 7 items, the raw scores vary from 7 to 35 and are converted to corresponding T-scores in the range of 29.4 (least fatigue) to 83.2 (most fatigue). TSQM transformed scores (T-scores) were measured on a 0–100 scale (0 = worst satisfaction and 100 = perfect satisfaction)
  2. CI confidence interval, GHP general health perception, IgG immunoglobulin G, OR odds ratio, PROMIS Patient-Reported Outcome Management Information System, SCIG subcutaneous immunoglobulin, SD standard deviation, TSQM Treatment Satisfaction Questionnaire for Medication
  3. aPredictor on an anchored numeric scale from 1 to 7 (1 = not very confident and 7 = very confident). The logistic regression yields an OR which predicts the likelihood of each category achieving the desired best tertile, and a significant OR > 1 implies higher odds than with the reference category. The least squares regression models score on a continuous linear scale using the original 1–7 scale, where a higher coefficient implies a higher GHP
  4. bRegression coefficient reported for a 0.5 SD increase in score (equivalent to 10 units)
  5. cRegression coefficient reported for a 0.5 SD increase in score (equivalent to 5 units). The model had an R2 = 36.2%, suggesting that over a third of scores can be explained by the factors in the final model