Journal of General Internal Medicine

, Volume 25, Issue 10, pp 1057–1063 | Cite as

Laboratory Test Ordering at Physician Offices with and without On-Site Laboratories

  • Tara F. BishopEmail author
  • Alex D. Federman
  • Joseph S. Ross
Original Research



Physician self-referral, ordering a test or procedure or referring to a facility in which a physician has a financial interest, has been associated with increased utilization of health care services.


To examine the association between on-site laboratories and laboratory test ordering among visits to group-practice physicians.


Cross-sectional study using data from the 2005 and 2006 National Ambulatory Medical Care Surveys.

Study Population

Visits by adults to non-federally-funded, non-hospital-based group practices. Primary analyses focused on visits to physician owners; secondary analyses focused on visits to non-owners.

Main Measures

Ordering of five laboratory tests: complete blood count (CBC), electrolytes, glycoslyated hemoglobin A1c (HbA1c), cholesterol, and prostate-specific antigen (PSA).

Key Results

There were 19,163 visits to group-practice owners with 51.9% to a practice with an on-site laboratory. Visits to primary care physicians were more likely to be to a practice with an on-site laboratory when compared with visits to specialists (64.4% vs. 34.0%, p < 0.001). Among visits to specialist group owners, all five tests were ordered more often if there was an on-site laboratory, even after accounting for patient and practice characteristics: CBC: adjusted odds ratio[OR] = 8.01, 95% Confidence Interval [CI], 5.00–12.82, p < 0.001; electrolytes: aOR = 3.51, 95% CI, 1.93–6.40, p < 0.001; HbA1c: aOR = 4.91, 95% CI, 1.75–13.78, p = 0.003; cholesterol: aOR = 3.32, 95% CI, 1.85–5.93, p < 0.001; and PSA: aOR = 3.84, 95% CI, 1.93–7.65, p < 0.001. This association was not found among visits to primary care physician owners and all practice non-owners (both primary care and specialists). The estimated excess spending on these five tests by specialist owners with on-site laboratories was $75 million per 100 million visits.


In a nationally representative sample of visits to physician-owned group practices, specialist owners with on-site laboratories were more likely to order five common laboratory tests, potentially resulting in millions in excess healthcare spending.


physician self-referral reimbursement/incentive laboratories/economics laboratories/utilization 



This project was not directly supported with external funds. Drs. Ross and Federman are both currently supported by the National Institute on Aging (K08 AG032886 and K23 AG028955-01, respectively) and by the American Federation of Aging Research through the Paul B. Beeson Career Development Award Program.

Conflict of Interest

None disclosed.


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Copyright information

© Society of General Internal Medicine 2010

Authors and Affiliations

  • Tara F. Bishop
    • 1
    Email author
  • Alex D. Federman
    • 1
  • Joseph S. Ross
    • 2
    • 3
  1. 1.Division of General Internal MedicineMount Sinai School of MedicineNew YorkUSA
  2. 2.Department of Geriatrics and Palliative MedicineMount Sinai School of MedicineNew YorkUSA
  3. 3.HSR&D Research Enhancement Award Program and Geriatrics Research, Education, and Clinical Center, James J. Peters Veterans Administration Medical CenterBronxUSA

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