Table 2.
Association between On-Site Laboratories and Test Ordering in Visits to Owner Physicians in Group Practices
| Test Ordered in Visits with No On-Site Lab, % (95% CI)a | Test Ordered in Visits with On-Site Lab, % (95% CI)a | Unadjusted OR (95% CI) | p value | Adjusted OR (95% CI)b | p value | |
|---|---|---|---|---|---|---|
| Visits to All Physicians (weighted n = 585 million) | ||||||
| CBC | 6.6 (5.1–8.5) | 19.2 (16.5–22.1) | 3.37 (2.45–4.65) | <0.001 | 2.53 (1.76–3.62) | <0.001 |
| Electrolytes | 3.8 (2.5–5.7) | 10.3 (7.8–13.4) | 2.87 (1.70–4.85) | <0.001 | 1.82 (1.08–3.06) | 0.03 |
| HbA1c | 1.7 (1.1–2.6) | 4.1 (3.3–5.1) | 2.44 (1.49–4.01) | <0.001 | 1.46 (0.88–2.41) | 0.14 |
| Cholesterol | 5.2 (4.0–6.8) | 12.7 (10.1–15.9) | 2.65 (1.76–3.99) | <0.001 | 1.49 (1.06–2.11) | 0.02 |
| PSA | 1.7 (1.1–2.5) | 3.7 (3.0–4.7) | 2.1 (1.3–3.3) | 0.002 | 1.97 (1.20–3.25) | 0.008 |
| Visits to Primary Care Physicians (weighted n = 266 million) | ||||||
| CBC | 16.9 (12.8–22.0) | 18.1 (14.9–21.8) | 1.09 (0.72–1.65) | 0.69 | 1.12 (0.75–1.67) | 0.59 |
| Electrolytes | 9.8 (5.8–16.0) | 11.1 (7.6–15.8) | 1.15 (0.55–2.38) | 0.71 | 1.14 (0.57–2.28) | 0.71 |
| HbA1c | 5.2 (3.4–8.0) | 5.1 (4.1–6.3) | 0.97 (0.58–1.65) | 0.92 | 0.99 (0.61–1.59) | 0.96 |
| Cholesterol | 15.1 (11.9–18.9) | 15.2 (12.1–18.9) | 1.01 (0.65–1.57) | 0.97 | 1.01 (0.67–1.52) | 0.95 |
| PSA | 3.4 (2.1–5.7) | 3.4 (2.5–4.5) | 0.98 (0.51–1.88) | 0.96 | 0.91 (0.46–1.81) | 0.79 |
| Visits to Specialist Physicians (weighted n = 319 million) | ||||||
| CBC | 2.8 (1.9–4.1) | 19.0 (14.1–25.2) | 8.11 (4.74–13.88) | <0.001 | 8.01 (5.00–12.82) | <0.001 |
| Electrolytes | 1.7 (1.0–3.0) | 6.0 (4.1–8.7) | 3.68 (1.83–7.38) | <0.001 | 3.51 (1.93–6.40) | <0.001 |
| HbA1c | 0.5 (0.2–1.1) | 1.9 (1.2–3.4) | 4.14 (1.40–12.23) | 0.01 | 4.91 (1.75–13.78) | 0.003 |
| Cholesterol | 1.7 (1.1–2.7) | 5.8 (3.8–8.5) | 3.50 (1.89–6.49) | <0.001 | 3.32 (1.85–5.93) | <0.001 |
| PSA | 1.1 (0.6–2.0) | 4.1 (2.8–6.0) | 3.90 (1.84–8.24) | 0.001 | 3.84 (1.93–7.65) | <0.001 |
aSurvey weighted percentages, age≥18, based on the U.S. population represented by the sample of visits for which data was collected
bAdjusted for patient sex, age, race, ethnicity, number of chronic conditions, major reason for visit, geographic region, urban or rural location, presence of an electronic medical record and primary care, and specialist physician (if applicable)