Table 2.
Covariate Balance across Treatment and Comparison Groups before and after Matching or Weighting on the Propensity Score
| Original Sample | Kernel Matched Sample | |||||
|---|---|---|---|---|---|---|
| Variable | Mean Treatment (n = 374) | Mean Comparison (n = 1,163) | Standardized Difference (%) | Mean Treatment (n = 373) | Mean Comparison (n = 1,163) | Standardized Difference (%) |
| Sociodemographics (yes/no) | ||||||
| Age 55–75 | 0.55 | 0.60 | −10.0 | 0.55 | 0.55 | 1.1 |
| Age > 75 | 0.11 | 0.10 | 3.2 | 0.12 | 0.12 | −1.8 |
| Female | 0.56 | 0.57 | −1.4 | 0.56 | 0.58 | −3.8 |
| Race – White | 0.66 | 0.77 | −24.1* | 0.66 | 0.66 | 0.7 |
| Race – Black | 0.29 | 0.18 | 27.4* | 0.29 | 0.30 | −1.1 |
| Education – College graduate or higher | 0.40 | 0.53 | −26.3* | 0.40 | 0.40 | 0.8 |
| Education – High school or some college | 0.54 | 0.42 | 23.9* | 0.54 | 0.54 | −0.4 |
| Medicare | 0.34 | 0.32 | 4.4 | 0.35 | 0.36 | −2.5 |
| Medicaid | 0.21 | 0.11 | 27.8* | 0.20 | 0.22 | −4.2 |
| Medication in week before hospitalization | ||||||
| Morphine equivalent dose (mg) | 26.51 | 12.46 | 31.0* | 25.31 | 23.29 | 4.5 |
| Advance care plans (yes/no) | ||||||
| Health care proxy | 0.45 | 0.52 | −15.1* | 0.45 | 0.46 | −1.7 |
| Living will | 0.39 | 0.45 | −12.4* | 0.39 | 0.39 | 0.0 |
| Help at home in 2 weeks prior to the hospitalization | ||||||
| Hours of home health aide help per week | 0.74 | 0.97 | −3.5 | 0.74 | 0.79 | −0.6 |
| Visiting nurse services (yes/no) | 0.15 | 0.12 | 7.3 | 0.15 | 0.15 | −0.5 |
| Illness and symptom severity measures† | ||||||
| Lymphoma/myeloma | 0.05 | 0.08 | −14.6* | 0.05 | 0.05 | −1.4 |
| Hospital complications before reference day | 0.03 | 0.08 | −20.1* | 0.03 | 0.04 | −1.2 |
| Number of Elixhauser‡ comorbidities | 4.06 | 3.20 | 43.7* | 4.05 | 3.98 | 3.9 |
| Needs complete assistance with 1+ ADL | 0.13 | 0.07 | 21.6* | 0.13 | 0.14 | −2.8 |
| Needs complete or partial assistance with bathing | 0.34 | 0.18 | 38.2* | 0.34 | 0.35 | −1.9 |
| Needs complete or partial assistance with transferring | 0.35 | 0.14 | 49.3* | 0.35 | 0.35 | 0.8 |
| Symptom severity at baseline | ||||||
| No. physical and psychological symptoms | 8.88 | 6.97 | 56.0* | 8.87 | 8.86 | 0.2 |
| Mean severity of physical symptoms§ | 1.90 | 1.32 | 68.8* | 1.90 | 1.91 | −1.0 |
| Mean severity of psychological symptoms§ | 1.59 | 1.45 | 11.2* | 1.58 | 1.53 | 4.4 |
| Symptom severity at reference day¶ | ||||||
| No. physical and psychological symptoms | 7.85 | 6.66 | 39.4* | 7.83 | 7.82 | 0.5 |
| Mean severity of physical symptoms§ | 1.82 | 1.34 | 63.7* | 1.82 | 1.79 | 3.6 |
| Mean severity of psychological symptoms§ | 1.39 | 1.03 | 29.5* | 1.39 | 1.45 | −4.9 |
| Pain: somewhat | 0.11 | 0.14 | −8.6 | 0.11 | 0.11 | 1.0 |
| Pain: quite a bit | 0.25 | 0.22 | 9.0 | 0.25 | 0.27 | −4.5 |
| Pain: very much | 0.33 | 0.17 | 36.3* | 0.33 | 0.30 | 7.3 |
| Fatigue: a little, somewhat, or quite a bit | 0.35 | 0.37 | −4.9 | 0.35 | 0.36 | −0.9 |
| Fatigue: very much | 0.31 | 0.18 | 29.3* | 0.31 | 0.31 | 0.3 |
*
Absolute value of mean standardized difference above 10%.
†
Measures are dichotomous unless otherwise indicated.
‡
Elixhauser comorbidity scale (Elixhauser et al. 1998).
§
Range 0–4; higher numbers indicate worse severity on Condensed Memorial Symptom Assessment Scale (Chang et al. 2004).
¶
Reference day refers to day of consult for treated patients. The reference day for usual care patients is the day in which they were most similar to treated patients based on symptom severity and sociodemographic characteristics.
ADL, activities of daily living.