Table 2.
Model Parameters, Base Case Values, and Ranges Used in Sensitivity Analyses (SA)
| Model Parameters | Base Case | Range for SA* | References |
|---|---|---|---|
| Clinical parameters, status quo scenario | |||
| Patients on antihyperglycemic medications at start of modeling period | 32% | 32–82% | Rodondi et al. (2006); Hoerger et al. (2008) |
| Adherence to HbA1c testing criterion: predicted mean time between HbA1c tests over 2 years† | Kerr et al. (2004); Hoerger et al. (2008) | ||
| ≤180 days | 15–20% | 15–60% | |
| >180 days | 55–56% | 45–56% | |
| No HbA1c tests | 24–30% | 14–30% | |
| Patients with time between HbA1c tests ≤180 days | |||
| First HbA1c ≥8%† | 22–25% | Saaddine et al. (2002); Rodondi et al. (2006); Saaddine et al. (2006); Hoerger et al. (2008) | |
| Adherence to medication initiation & adjustment criteria | Rodondi et al. (2006); Schmittdiel et al. (2008) | ||
| Medications initiated when first HbA1c ≥8% | 79% | 79–99% | |
| Medications adjusted when first HbA1c ≥8% | 58% | 58–78% | |
| Patients with time between HbA1c tests >180 days | |||
| First HbA1c ≥8%† | 37–50% | Saaddine et al. (2002); Rodondi et al. (2006); Saaddine et al. (2006); Hoerger et al. (2008) | |
| Adherence to medication initiation & adjustment criteria | Berlowitz et al. (2005); Rodondi et al. (2006); Schmittdiel et al. (2008) | ||
| Medications initiated when first HbA1c ≥8% | 24% | 24–44% | |
| Medications Adjusted When First HbA1c ≥8% | 29% | 29–49% | |
| HbA1c outcomes at end of modeling period | |||
| Mean HbA1c including imputed values | 7.8% | ||
| Mean HbA1c for patients with tests | 6.8% | ||
| Distribution of HbA1c for patients with tests | |||
| HbA1c ≥8% | 38% | Hoerger et al. (2008) | |
| HbA1c 7% to <8% | 24% | ||
| HbA1c <7% | 38% | ||
| Distribution of imputed values | Rossi et al. (2008) | ||
| HbA1c ≥8% | 37–50% | 17–50% | |
| HbA1c 7% to <8% | 13–21% | 13–31% | |
| HbA1c <7% | 37–42% | 37–52% | |
| Supplemental analysis: severe hyper- & hypoglycemia† | |||
| Severe hypoglycemic events, annual rate | 0.02–0.78% | Bolen et al. (2007); Bodmer et al. (2008); Kelly et al. (2009) | |
| Severe hyperglycemic events, annual rate | 0.36–1.34% | Wang et al. (2009) | |
| Clinical parameters, improved care scenario | |||
| Adherence to HbA1c testing criterion: time between tests ≤180 Days | 100% | ||
| Adherence to medication initiation & adjustment criteria | 100% | ||
| Assumed decline in HbA1c due to improved care | UK Prospective Diabetes Study (UKPDS) Group (1998); Shojania et al. (2006) | ||
| Status quo HbA1c ≥10% | −1% | −2.5–0.5% | |
| Status quo HbA1c ≥8% to <10% | −1% | −1–0.5% | |
| Status quo HbA1c 7% to <8% | −0.5% | −0.5–0% | |
| HbA1c outcomes at end of modeling period | |||
| Mean HbA1c including imputed values | 7.5% | 7.2–7.7% | |
| Mean HbA1c for patients with tests | 6.4% | 6.2–6.5% | |
| Supplemental analysis: severe hyper- & hypoglycemia | |||
| Severe hypoglycemic events, annual rate | 0.04–2.34% | Duckworth et al. (2008); Kelly et al. (2009) | |
| Severe hyperglycemic events, annual rate | 0.52–0.62% | Wang et al. (2009) | |
| Costs of glucose management, both scenarios (2009 U.S. dollars) | |||
| Associated with each HbA1c test | |||
| 1 level 2 physician visit (CPT 99212) | U.S.$37.15 | Medicare Physician Fee Schedule Look-Up [database online] (2009) | |
| 1 HbA1c laboratory test (CPT 83036) | U.S.$14.17 | Medicare Clinical Laboratory Fee Schedule [database online] (2009) | |
| Associated with medication initiation and adjustment | |||
| 1 level 4 physician visit (CPT 99214) | U.S.$92.33 | Medicare Physician Fee Schedule Look-Up [database online] (2009) | |
| Daily medication costs | U.S.$3.56 | U.S.$1.42–U.S.$9.13 | Alexander et al. (2008); Kahn et al. (2008) |
| Supplemental analysis: severe hyper- & hypoglycemia | |||
| Associated with each severe hypoglycemic event, level 5 physician visit (CPT 99215 or 99285) | U.S.$124.79–170.23 | Medicare Physician Fee Schedule Look-Up [database online] (2009) | |
| Associated with each severe hyperglycemic event, hospitalization | U.S.$14,501–U.S.$21,775 | Kim (2007); U.S. Department of Labor: Bureau of Labor Statistics (2007) | |
*
Sensitivity analysis ranges were tailored to the base case value for each specific branch of the probability model and varied in a comparable fashion across the branches.
†
In the probability model, patients were initially stratified by whether they were on antihyperglycemic medications or not at study entry; the range of base case values refers to these two groups.
‡
See Appendix SA2 for details.