• Victoria Valencia, Vineet M Arora, Sumant R Ranji, Carlos Meza, and Christopher Moriates.
• Department of Internal Medicine, Dell Medical School at The University of Texas at Austin.
• JAMA Intern Med. 2018 Jan 1; 178 (1): 39-47.

ImportanceRobust laboratory use data are lacking to support the general assumption that teaching hospitals with trainees routinely order more laboratory tests for inpatients than do nonteaching hospitals.ObjectiveTo quantify differences in the use of laboratory tests between teaching and nonteaching hospitals.Design, Setting, And ParticipantsA cross-sectional study was performed using a statewide database to identify hospitalizations with a primary diagnosis of bacterial pneumonia or cellulitis from January 1, 2014, to June 30, 2015, at teaching and nonteaching hospitals with 100 or more hospitalizations of each condition. Patients included were adult inpatients with a primary diagnosis of bacterial pneumonia (n = 24 118) or cellulitis (n = 19 211); patients excluded were those with an intensive care unit stay, transfer from another hospital, or a length of stay that was 2 SDs or more of the condition's mean length of stay.Main Outcomes And MeasuresMean laboratory tests per day stratified by illness severity, as well as factors associated with laboratory use rates.ResultsA total of 43 329 hospitalized patients (20493 women and 22836 men) had a principal diagnosis of bacterial pneumonia or cellulitis across 11 major teaching hospitals, 12 minor teaching hospitals, and 73 nonteaching hospitals in Texas. Mean number of laboratory tests per day varied significantly by hospital type and was highest for major teaching hospitals for both conditions (bacterial pneumonia: major teaching hospitals, 13.21; 95% CI, 12.91-13.51; nonteaching hospitals, 8.92; 95% CI, 8.84-9.00; P < .001; cellulitis: major teaching hospitals, 10.43; 95% CI, 10.16-10.70; nonteaching hospitals, 7.29; 95% CI, 7.22-7.36; P < .001). This association held for all levels of illness severity for both conditions, except for patients with cellulitis with the highest illness severity level. In generalized mixed linear regression models, controlling for additional patient and encounter covariates, there was a significant difference in the marginal effect of hospital teaching status on mean number of laboratory tests per day between major teaching and nonteaching hospitals (difference in marginal mean laboratory tests per day for bacterial pneumonia, 3.58; 95% CI, 2.61-4.55; P < .001; for cellulitis, 2.61; 95% CI, 1.76-3.47; P < .001).Conclusions And RelevanceCompared with nonteaching hospitals, patients in Texas admitted to major teaching hospitals with bacterial pneumonia or cellulitis received significantly more laboratory tests after controlling for illness severity, length of stay, and patient demographics. These results support the need to examine how the culture of training environments may contribute to increased use of laboratory tests.

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