Community health workers as change agents in improving equity in birth outcomes in Detroit.

We examined whether pairing pregnant women with community health workers improved pregnancy outcomes among 254 Black women with singleton pregnancies participating in the Women-Inspired Neighborhood (WIN) Network: Detroit using a case-control design. A subset (N = 63) of women were recontacted and asked about program satisfaction, opportunities, and health behaviors. Michigan Vital Statistics records were used to ascertain controls (N = 12,030) and pregnancy and infant health outcomes. Logistic and linear regression were used to examine the association between WIN Network participation and pregnancy and infant health outcomes. The WIN Network participants were less likely than controls to be admitted to the neonatal intensive care unit (odds ratio = 0.55, 95% CI 0.33-0.93) and had a longer gestational length (mean difference = 0.42, 95% CI 0.02-0.81). Community health workers also shaped participants' view of opportunities to thrive. This study demonstrates that community health workers can improve pregnancy outcomes for Black women.

Analysis of Factors Associated with Return-to-Work After Lumbar Surgery up to 2-Years Follow-up: A Michigan Spine Surgery Improvement Collaborative (MSSIC) Study.

STUDY DESIGN: Michigan Spine Surgery Improvement Collaborative (MSSIC) prospectively collects data on all patients undergoing operations for degenerative and/or deformity indications. OBJECTIVE: We aimed to identify which factors are significantly associated with return-to-work after lumbar surgery at long-term follow-up. SUMMARY OF BACKGROUND DATA: Prior publications have created a clinically relevant predictive model for return-to-work, wherein education, gender, race, comorbidities, and preoperative symptoms increased likelihood of return-to-work at 3 months after lumbar surgery. We sought to determine if these trends 1) persisted at 1 year and 2 years postoperatively; or 2) differed among preoperatively employed versus unemployed patients. METHODS: MSSIC was queried for all patients undergoing lumbar operations (2014-2019). All patients intended to return-to-work postoperatively. Patients were followed for up to 2 years postoperatively. Measures of association were calculated with multivariable generalized estimating equations. RESULTS: Return-to-work increased from 63% (3542/5591) at 90 days postoperatively to 75% (3143/4147) at 1 year and 74% (2133/2866) at 2 years postoperatively. Following generalized estimating equations, neither clinical nor surgical variables predicted return-to-work at all three time intervals: 90 days, 1 year, and 2 years postoperatively. Only socioeconomic factors reached statistical significance at all follow-up points. Preoperative employment followed by insurance status had the greatest associations with return-to-work. In a subanalysis of patients who were preoperatively employed, insurance was the only factor with significant associations with return-to-work at all three follow-up intervals. The return-to-work rates among unemployed patients at baseline increased from 29% (455/1100) at 90 days, 44% (495/608) at 1 year, and 46% (366/426) at 2 years postoperatively. The only two significant factors associated with return-to-work at all three follow-up intervals were Medicaid, as compared with private insurance, and male gender. CONCLUSION: In patients inquiring about long-term return-to-work after lumbar surgery, insurance status represents the important determinant of employment status.Level of Evidence: 2.

The association of patient education level with outcomes after elective lumbar surgery: a Michigan Spine Surgery Improvement Collaborative study.

OBJECTIVE: Socioeconomic factors have been shown to impact a host of healthcare-related outcomes. Level of education is a marker of socioeconomic status. This study aimed to investigate the relationship between patient education level and outcomes after elective lumbar surgery and to characterize any education-related disparities. METHODS: The Michigan Spine Surgery Improvement Collaborative registry was queried for all lumbar spine operations. Primary outcomes included patient satisfaction determined by the North American Spine Society patient satisfaction index, and reaching the minimum clinically important difference of Patient-Reported Outcomes Measurement Information System Physical Function score and return to work up to 2 years after surgery. Multivariate Poisson generalized estimating equation models reported adjusted risk ratios. RESULTS: A total of 26,229 lumbar spine patients had data available for inclusion in this study. On multivariate generalized estimating equation analysis all comparisons were done versus the high school (HS)/general equivalency development (GED)-level cohort. For North American Spine Society satisfaction scores after surgery the authors observed the following: at 90 days the likelihood of satisfaction significantly decreased by 11% (p < 0.001) among < HS, but increased by 1% (p = 0.52) among college-educated and 3% (p = 0.011) among postcollege-educated cohorts compared to the HS/GED cohort; at 1 year there was a decrease of 9% (p = 0.02) among < HS and increases of 3% (p = 0.02) among college-educated and 9% (p < 0.001) among postcollege-educated patients; and at 2 years, there was an increase of 5% (p = 0.001) among postcollege-educated patients compared to the < HS group. The likelihood of reaching a minimum clinically important difference of Patient-Reported Outcomes Measurement Information System Physical Function score at 90 days increased by 5% (p = 0.005) among college-educated and 9% (p < 0.001) among postcollege-educated cohorts; at 1 year, all comparison cohorts demonstrated significance, with a decrease of 12% (p = 0.007) among < HS, but an increase by 6% (p < 0.001) among college-educated patients and 14% (p < 0.001) among postcollege-educated compared to the HS/GED cohort; at 2 years, there was a significant decrease by 19% (p = 0.003) among the < HS cohort, an increase by 8% (p = 0.001) among the college-educated group, and an increase by 16% (p < 0.001) among the postcollege-educated group. For return to work, a significant increase was demonstrated at 90 days and 1 year when comparing the HS or less group with college or postcollege cohorts. CONCLUSIONS: This study demonstrated negative associations on all primary outcomes with lower levels of education. This finding suggests a potential disparity linked to education in elective spine surgery.

Disparities in outcomes after spine surgery: a Michigan Spine Surgery Improvement Collaborative study.

OBJECTIVE: Most studies on racial disparities in spine surgery lack data granularity to control for both comorbidities and self-assessment metrics. Analyses from large, multicenter surgical registries can provide an enhanced platform for understanding different factors that influence outcome. In this study, the authors aimed to determine the effects of race on outcomes after lumbar surgery, using patient-reported outcomes (PROs) in 3 areas: the North American Spine Society patient satisfaction index, the minimal clinically important difference (MCID) on the Oswestry Disability Index (ODI) for low-back pain, and return to work. METHODS: The Michigan Spine Surgery Improvement Collaborative was queried for all elective lumbar operations. Patient race/ethnicity was categorized as Caucasian, African American, and "other." Measures of association between race and PROs were calculated with generalized estimating equations (GEEs) to report adjusted risk ratios. RESULTS: The African American cohort consisted of a greater proportion of women with the highest comorbidity burden. Among the 7980 and 4222 patients followed up at 1 and 2 years postoperatively, respectively, African American patients experienced the lowest rates of satisfaction, MCID on ODI, and return to work. Following a GEE, African American race decreased the probability of satisfaction at both 1 and 2 years postoperatively. Race did not affect return to work or achieving MCID on the ODI. The variable of greatest association with all 3 PROs at both follow-up times was postoperative depression. CONCLUSIONS: While a complex myriad of socioeconomic factors interplay between race and surgical success, the authors identified modifiable risk factors, specifically depression, that may improve PROs among African American patients after elective lumbar spine surgery.

Association Between Implementation of a Universal Face Mask Policy for Healthcare Workers in a Health Care System and SARS-CoV-2 Positivity Testing Rate in Healthcare Workers.

OBJECTIVE: Examine the effect of a universal facemask policy for healthcare workers (HCW) and incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positivity. METHODS: Daily number of symptomatic HCW tested, SARS-CoV-2 positivity rates, and HCW job-descriptions were collected pre and post Universal HCW facemask policy (March 26, 2020). Multiple change point regression was used to model positive-test-rate data. SARS-CoV-2 testing and positivity rates were compared for pre-intervention, transition, post-intervention, and follow-up periods. RESULTS: Between March 12 and August 10, 2020, 19.2% of HCW were symptomatic for COVID-19 and underwent SARS-CoV-2 testing. A single change point was identified ∼March 28-30 (95% probability). Before the change point, the odds of a tested HCW having a positive result doubled every 4.5 to 7.5 days. Post-change-point, the odds of a tested HCW having a positive result halved every 10.5 to 13.5 days. CONCLUSIONS: Universal facemasks were associated with reducing HCW's risk of acquiring COVID-19.

Cost of hospitalization for aneurysmal subarachnoid hemorrhage in the United States.

OBJECTIVE: Recent large-scale studies describing hospitalization cost trends secondary to aneurysmal subarachnoid hemorrhage (aSAH) in the United States are lacking. We sought to discover the impact of aSAH-related factors upon its hospitalization cost. PATIENTS AND METHODS: Patients with a primary diagnosis of aSAH were selected utilizing the National Inpatient Sample. Regression analyses were used to evaluate the impact of aSAH-related factors on hospitalization costs. RESULTS: From 2002-2014, 22,831 cases of aSAH were identified. The inflation-adjusted mean cost of hospitalization was $82,514 (standard deviation ± $54,983). The proportion of males was lower (31%), but a higher cost of $3385 (± $685; p < .001) remained compared to females. Median length of hospitalization was 16 days (interquartile range 11-23) and each day increase in hospitalization was associated with a cost increase of $3228 (± $19; p < .001). There was no difference in cost between patients undergoing aneurysmal coiling or clipping. When compared to patients < 40 years old, the increase in cost for patients 40-59 years old was $3829 (± $914; p < .001), and $4573 (± $1033; p < .001) for patients 60-79 years old; however, for patients ≥ 80 years old, there was a decrease in cost of $8124 (± $1722; p < .001). Several central nervous system complications were also associated with increased cost. CONCLUSION: aSAH is a significant financial burden on the United States healthcare system. We were able to identify many important factors associated with higher costs, and these results may help us understand resource utilization and develop future cost-reduction strategies.

Assessment methods and resource requirements for milestone reporting by an emergency medicine clinical competency committee.

BACKGROUND: The Accreditation Council for Graduate Medical Education (ACGME) introduced milestones for Emergency Medicine (EM) in 2012. Clinical Competency Committees (CCC) are tasked with assessing residents on milestones and reporting them to the ACGME. Appropriate workflows for CCCs are not well defined. OBJECTIVE: Our objective was to compare different approaches to milestone assessment by a CCC, quantify resource requirements for each and to identify the most efficient workflow. DESIGN: Three distinct processes for rendering milestone assessments were compared: Full milestone assessments (FMA) utilizing all available resident assessment data, Ad-hoc milestone assessments (AMA) created by multiple expert educators using their personal assessment of resident performance, Self-assessments (SMA) completed by residents. FMA were selected as the theoretical gold standard. Intraclass correlation coefficients were used to analyze for agreement between different assessment methods. Kendall's coefficient was used to assess the inter-rater agreement for the AMA. RESULTS: All 13 second-year residents and 7 educational faculty of an urban EM Residency Program participated in the study in 2013. Substantial or better agreement between FMA and AMA was seen for 8 of the 23 total subcompetencies (PC4, PC8, PC9, PC11, MK, PROF2, ICS2, SBP2), and for 1 subcompetency (SBP1) between FMA and SMA. Multiple AMA for individual residents demonstrated substantial or better interobserver agreement in 3 subcompetencies (PC1, PC2, and PROF2). FMA took longer to complete compared to AMA (80.9 vs. 5.3 min, p < 0.001). CONCLUSIONS: Using AMA to evaluate residents on the milestones takes significantly less time than FMA. However, AMA and SMA agree with FMA on only 8 and 1 subcompetencies, respectively. An estimated 23.5 h of faculty time are required each month to fulfill the requirement for semiannual reporting for a residency with 42 trainees.

Mechanomyography for Intraoperative Assessment of Cortical Breach During Instrumented Spine Surgery.

OBJECTIVE: We sought to determine the utility of mechanomyography (MMG) in detecting and preventing pedicle breach in instrumented lumbar spine surgery. METHODS: In a prospective nonrandomized trial without controls, we selected consecutive patients to undergo intraoperative MMG during instrumented lumbar spine surgery. MMG testing was performed at the original pilot hole, after tapping, and after screw placement, with the minimum current to elicit a recorded MMG response. All patients underwent a postoperative computed tomography scan, and a single radiologist interpreted each pedicle to identify breach. Chi-square test was used to compare patients with and without breaches. Two sample Student's t-tests were used to compare changes in functional outcomes. Sensitivity and specificity of MMG were computed using receiver operating characteristic curve analysis. RESULTS: There were 122 consecutive instrumented lumbar surgery patients enrolled, with a total of 890 lumbar pedicle screws tested with MMG. The medial or inferior breach rate was 2.25%, with no statistically significant difference in Oswestry Disability Index or visual analog scale between patients who breached and who did not. For the MMG measurement from the original pilot hole, the area under the receiver operating characteristic was 0.835; the maximum combination of sensitivity (80.42%) and specificity (80.6%) was found using MMG current ≤12 mA. We found that an MMG cutoff of >12 mA resulted in a 99.5% likelihood of no medial or inferior breach. CONCLUSIONS: MMG can be safely used during instrumented lumbar spine surgery. A cutoff value of >12 mA for MMG can accurately predict and prevent medial and inferior pedicle screw breach.

Assessment of radiographic and clinical outcomes of an articulating expandable interbody cage in minimally invasive transforaminal lumbar interbody fusion for spondylolisthesis.

OBJECTIVE The inability to significantly improve sagittal parameters has been a limitation of minimally invasive surgery for transforaminal lumbar interbody fusion (MIS TLIF). Traditional cages have a limited capacity to restore lordosis. This study evaluates the use of a crescent-shaped articulating expandable cage (Altera) for MIS TLIF. METHODS This is a retrospective review of 1- and 2-level MIS TLIF. Radiographic outcomes included differences in segmental and lumbar lordosis, disc height, evidence of fusion, and any endplate violations. Clinical outcomes included the numeric rating scale for leg and back pain and the Oswestry Disability Index (ODI) for low-back pain. RESULTS Thirty-nine patients underwent single-level MIS TLIF, and 5 underwent 2-level MIS TLIF. The mean age was 63.1 years, with 64% women. On average, spondylolisthesis was corrected by 4.3 mm (preoperative = 6.69 mm, postoperative = 2.39 mm, p < 0.001), the segmental angle was improved by 4.94° (preoperative = 5.63°, postoperative = 10.58°, p < 0.001), and segmental height increased by 3.1 mm (preoperative = 5.09 mm, postoperative = 8.19 mm, p < 0.001). At 90 days after surgery the authors observed the following: a smaller postoperative sagittal vertical axis was associated with larger changes in back pain at 90 days (r = -0.558, p = 0.013); a larger decrease in spondylolisthesis was associated with greater improvements in ODI and back pain scores (r = -0.425, p = 0.043, and r = -0.43, p = 0.031, respectively); and a larger decrease in pelvic tilt (PT) was associated with greater improvements in back pain (r = -0.548, p = 0.043). For the 1-year PROs, the relationship between the change in PT and changes in ODI and numeric rating scale back pain were significant (r = 0.612, p = 0.009, and r = -0.803, p = 0.001, respectively) with larger decreases in PT associated with larger improvements in ODI and back pain. Overall for this study there was a 96% fusion rate. Fourteen patients were noted to have endplate violation on intraoperative fluoroscopy during placement of the cage. Only 3 of these had progression of their subsidence, with an overall subsidence rate of 6% (3 of 49) visible on postoperative CT. CONCLUSIONS The use of this expandable, articulating, lordotic, or hyperlordotic interbody cage for MIS TLIF provides a significant restoration of segmental height and segmental lordosis, with associated improvements in sagittal balance parameters. Patients treated with this technique had acceptable levels of fusion and significant reductions in pain and disability.

PROMIS evaluation for head and neck cancer patients: a comprehensive quality-of-life outcomes assessment tool.

OBJECTIVES/HYPOTHESIS: The objective of this study was to evaluate the Patient-Reported Outcomes Measure Information System (PROMIS) in a head and neck cancer patient cohort by assessing the associations of the PROMIS instruments with the responses to the European Oncology Research and Treatment of Cancer (EORTC) general measures, EORTC head and neck (H&N) measures, and Voice Handicap Index (VHI-10). We hypothesized that PROMIS scores are related to the other measures and may be used as assessment tools to help determine quality-of-life outcomes in head and neck cancer patients. STUDY DESIGN: Prospective baseline assessment of quality-of-life outcomes. METHODS: Thirty-nine head and neck cancer patients were included in the study. PROMIS (domains of fatigue, physical functioning, sleep disturbance, sleep-related impairment, and negative perceived cognitive function, EORTC (general), EORTC H&N, and the VHI-10 were given to all patients at the onset of their cancer diagnosis. Spearman correlation coefficients were computed to assess relationships between the measures. Correlations with corresponding P values <.0083 (Bonferroni adjustment) were considered statistically significant. Descriptive statistics of means, standard deviations, medians, and ranges were computed for all the instruments and measures. RESULTS: Significant correlations between the PROMIS instruments and EORTC functional scales were observed. The PROMIS instruments were also associated with some of the EORTC symptom scales, as well as some of the EORTC H&N symptoms measures. PROMIS fatigue instrument was significantly correlated with the VHI-10 measure. CONCLUSIONS: PROMIS instruments are reasonable measures to determine quality-of-life outcomes in head and neck cancer patients. Computerized adaptive testing devices can be effectively utilized in this patient population. LEVEL OF EVIDENCE: 2c.

An assessment of MEG coherence imaging in the study of temporal lobe epilepsy.

PURPOSE: This study examines whether magnetoencephalographic (MEG) coherence imaging is more sensitive than the standard single equivalent dipole (ECD) model in lateralizing the site of epileptogenicity in patients with drug-resistant temporal lobe epilepsy (TLE). METHODS: An archival review of ECD MEG analyses of 30 presurgical patients with TLE was undertaken with data extracted subsequently for coherence analysis by a blinded reviewer for comparison of accuracy of lateralization. Postoperative outcome was assessed by Engel classification. MEG coherence images were generated from 10 min of spontaneous brain activity and compared to surgically resected brain areas outlined on each subject's magnetic resonance image (MRI). Coherence values were averaged independently for each hemisphere to ascertain the laterality of the epileptic network. Reliability between runs was established by calculating the correlation between epochs. Match rates compared the results of each of the two MEG analyses with optimal postoperative outcome. KEY FINDINGS: The ECD method provided an overall match rate of 50% (13/16 cases) for Engel class I outcomes, with 37% (11/30 cases) found to be indeterminate (i.e., no spikes identified on MEG). Coherence analysis provided an overall match rate of 77% (20/26 cases). Of 19 cases without evidence of mesial temporal sclerosis, coherence analysis correctly lateralized the side of TLE in 11 cases (58%). Sensitivity of the ECD method was 41% (indeterminate cases included) and that of the coherence method 73%, with a positive predictive value of 70% for an Engel class Ia outcome. Intrasubject coherence imaging reliability was consistent from run-to-run (correlation > 0.90) using three 10-min epochs. SIGNIFICANCE: MEG coherence analysis has greater sensitivity than the ECD method for lateralizing TLE and demonstrates reliable stability from run-to-run. It, therefore, improves upon the capability of MEG in providing further information of use in clinical decision-making where the laterality of TLE is questioned.

Development of a scoring system for atrial fibrillation in acute stroke and transient ischemic attack patients: the LADS scoring system.

INTRODUCTION: Detection of atrial fibrillation in patients presenting with ischemic stroke or transient ischemic attack (TIA) is important for the prevention of future events. We sought to develop a scoring system that would identify those patients most likely to have atrial fibrillation. METHODS: Records from an inpatient stroke and TIA database and echocardiographic data were reviewed. Consecutive acute stroke and TIA patients over the age of 18 who were admitted during a two-year period were studied. Univariate and multivariable analyses were performed to identify variables associated with atrial fibrillation. Logistic regression analyses were used to develop a scoring system for atrial fibrillation. RESULTS: 953 patient charts were reviewed; 145 patients (15%) had atrial fibrillation. In univariate and multivariate analyses, variables that were significantly associated with atrial fibrillation included left atrial diameter, age, and diagnosis of stroke. A history of smoking showed an inverse association. A 6-point scoring system based on these variables (with the acronym of LADS) was developed. A score of 4 or greater was associated with a sensitivity of 85.5% and a specificity of 53.1%. Approximately 47% of stroke and TIA patients would be excluded from further investigation using this score. CONCLUSIONS: We describe a system of scoring that identifies acute stroke and TIA patients with a greater chance of having atrial fibrillation. An inverse relationship with smoking was found. Further prospective studies are required to determine the clinical utility and cost-effectiveness of this scoring system in clinical practice and to investigate the inverse relationship between smoking and atrial fibrillation in this population.

Measuring adherence and persistence to disease-modifying agents among patients with relapsing remitting multiple sclerosis.

OBJECTIVES: To measure disease-modifying agent adherence and persistence among patients with multiple sclerosis (MS). DESIGN: Retrospective cohort study. SETTING: Multispecialty, salaried group practice in southeast Michigan, between June 1, 2004, and June 30, 2006. PATIENTS: 224 insured adult patients with relapsing remitting MS with an outpatient visit. MAIN OUTCOME MEASURES: Medical record-documented receipt of medication recommendation and prescription. Pharmacy claims data-derived measures of dispensing and among patients with two or more dispensings, medication possession ratios (MPRs), and proportion of gap days were estimated. Among those initiating agent use, persistence was estimated. RESULTS: Mean cohort age was 47.6 years, while 77% of participants were women and 39% were black. Of patients, 81.8% had a recommendation for a disease-modifying agent, 75.0% had a prescription, and 66.5% had two or more dispensings. Among those with two or more dispensings, mean MPR between the first and last dispensing date was 83.8% (95% CI 80.8-86.8), while mean MPR for the entire 24-month period was 68.0% (64.4-71.7). MPR for the 24-month period decreased with increasing drug copayments and was lower among black patients, while MPR between the first and last dispensing date increased with increasing age. Among those initiating therapy, 43% were nonpersistent with medications within 14 months. CONCLUSION: Medication adherence and persistence among patients with relapsing remitting MS is far from monolithic. Measuring medication adherence and persistence among defined populations is useful for understanding the relationship between medication use and outcomes in practice and for targeting patients and programs to improve medication adherence.

What do medical records tell us about potentially harmful co-prescribing?

BACKGROUND: Previous efforts document drug-drug interactions in ambulatory care. Yet little is known about medical record documentation or clinical management when interacting medications are received. METHODS: The study population was identified from the HMO Research Network's Centers for Education and Research on Therapeutics (n = 2,020,037). A random subsample of patients > or = 18 years of age with drug coverage in 2000 initiating a co-dispensing for (1) warfarin with a nonsteroidal anti-inflammatory drug (n = 97), (2) digoxin with verapamil or diltiazem (n = 100), or (3) lovastatin/simvastatin with diltiazem or verapamil (n = 89) was identified. RESULTS: The majority (63%-74%) of patients had documentation indicating receipt of both drugs during a single office visit. Documentation of risks and patient education was less common (< or = 14%, with all corresponding upper bounds of the 95% CIs < 23%). Clinical management changes were more frequently documented, ranging from 64% (95% CI: 47-81%) for lovastatin/simvastatin patients to 79% (95% CI: 60-99%) for warfarin patients. CONCLUSIONS: The findings, although indicating that clinicians are likely aware of concomitant receipt of interacting medications, call into question the adequacy of medical record documentation as well as clinical management when interacting drugs are co-prescribed in the ambulatory setting.

The utility of administrative data for measuring adherence to cancer surveillance care guidelines.

BACKGROUND: Adherence to professional society guidelines for follow-up or surveillance care in cancer survivors usually is measured with medical record review. Administrative data represent an alternative approach that may encompass larger numbers of patients with relatively low incremental costs. OBJECTIVES: We sought to determine the feasibility of using claims data to measure guideline adherence. METHODS: By reviewing paper and electronic medical records and claims data of 429 patients with 1 of 5 common cancers who received treatment with curative intent, we compared specific procedure receipt as well as guideline adherence classification as derived from claims and medical record data. Concordance was measured via kappa statistics. MEASURES: Care in the initial 18-month follow-up period was characterized as less than recommended, recommended, or greater than recommended per practice guidelines in both medical record and administrative data. RESULTS: Matching rates for individual procedures varied and were generally highest for certain laboratory tests and lowest for physical examinations. There were generally good-to-excellent levels of agreement (kappa=0.34-0.96) between a patient's classification in claims data and medical record data. No consistent differences in agreement were observed according to insurance type. CONCLUSIONS: In general, claims data capturing procedures and visit use for characterizing guideline adherence was comparable with what was documented in the medical record and suggests that if validated in other settings, administrative data could be used to describe patterns of follow up care.

Potential drug-drug interactions in the outpatient setting.

BACKGROUND: Although medication safety research has tended to focus on inpatients, the safety of drug use among outpatients is also a concern. OBJECTIVE: We estimate the frequency of potentially interacting concomitant medication dispensing among outpatients. RESEARCH DESIGN: We report the number and percent of patients annually dispensed an object drug of interest (ie, warfarin, digoxin, cyclosporine, or lovastatin/simvastatin) with a potentially interacting drug among a random sample of insured adults receiving care from 10 integrated delivery systems. We use 2 definitions of concomitant dispensing: medications dispensed: 1) during the time period for which the patient had the other medication available ('days supply') and 2) on the same day. We also estimate the number of insured U.S. population codispensed these medication pairs. RESULTS: Among patients dispensed a drug of interest, between 17.8% (95% confidence interval [CI]=17.1-18.6%) and 28.0% (95% CI=24.0-32.1%) were concomitantly dispensed a potentially interacting drug using the "days supply" definition, and between 7.1% (95% CI=6.6-7.7%) and 17.7% (95% CI=14.4-21.1%) using the "same day" definition. Extrapolating to the insured U.S. population, between 1.29 (95% CI=1.25-1.33; same day) and 2.67 (95% CI=2.62-2.72; days supply) million insured adults are dispensed 1 of these 4 potentially interacting pairs. CONCLUSIONS: We found evidence of potentially interacting concomitant medication dispensing among outpatients. An opportunity exists to better understand how such dispensing translates into adverse events and ultimately to improved medication safety.