<p><strong>Importance: </strong>While the 2016 US Centers for Disease Control and Prevention (CDC) guideline for prescribing opioids for chronic pain was not intended to address postoperative pain management, observers have noted the potential for the guideline to have affected postoperative opioid prescribing.</p>

<p><strong>Objective: </strong>To assess changes in postoperative opioid dispensing after vs before the CDC guideline release in March 2016.</p>

<p><strong>Design, Setting, and Participants: </strong>This cross-sectional study included 361 556 opioid-naive patients who received 1 of 8 common surgical procedures between March 16, 2014, and March 15, 2018. Data were retrieved from a private insurance database, and a retrospective interrupted time series analysis was conducted. Data analysis was conducted from March 2014 to April 2018.</p>

<p><strong>Exposure: </strong>Outcomes were measured before and after release of the 2016 CDC guideline.</p>

<p><strong>Main Outcomes and Measures: </strong>The primary outcome was the total amount of opioid dispensed in the first prescription filled within 7 days following surgery in morphine milligram equivalents (MMEs); secondary outcomes included the total amount of opioids prescribed and the incidence of any opioid refilled within 30 days after surgery. To characterize absolute opioid dispensing levels, the amount dispensed in initial prescriptions was compared with available procedure-specific recommendations.</p>

<p><strong>Results: </strong>The sample included 361 556 opioid-naive patients undergoing 8 general and orthopedic surgical procedures; 164 009 (45.4%) were male patients, and the median (interquartile range) age of the sample was 58 (45 to 69) years. The total amount of opioids dispensed in the first prescription after surgery decreased in the 2 years following the CDC guideline release, compared with an increasing trend in the 2 years prior (prerelease trend: 1.43 MME/month; 95% CI, 0.62 to 2.24 MME/month; P = .001; postrelease trend: -2.18 MME/month; 95% CI, -3.01 to -1.35 MME/month; P &lt; .001; trend change: -3.61 MME/month; 95% CI, -4.87 to -2.35 MME/month; P &lt; .001). Changes in initial dispensing amount trends were greatest for patients undergoing hip or knee replacement (-8.64 MME/month; 95% CI, -11.68 to -5.60 MME/month; P &lt; .001). Minimal changes were observed in rates of refills over time (net change: 0.14% per month; 95% CI, 0.06% to 0.23% per month; P = .001). Absolute amounts prescribed remained high throughout the period, with nearly half of patients (47.7%; 95% CI, 47.4%-47.9%) treated in the postguideline period receiving at least twice the initial opioid dose anticipated to treat postoperative pain based on available procedure-specific recommendations.</p>

<p><strong>Conclusions and Relevance: </strong>In this study, opioid dispensing after surgery decreased substantially after the 2016 CDC guideline release, compared with an increasing trend during the 2 years prior. Absolute amounts prescribed for surgery remained high during the study period, supporting the need for further efforts to improve postoperative pain management.</p>

<p><strong>PURPOSE: </strong>This study aimed to evaluate the accuracy of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis code for small for gestational age (SGA) recorded in administrative healthcare records using birthweight and gestational age information recorded in electronic medical records.</p>

<p><strong>METHODS: </strong>We used billing and medical records from women aged 13-55 years who delivered at a tertiary care center in the USA between 2004 and 2011. Information on birthweight, gestational age at birth, and ICD-9-CM code for SGA, 656.5x, was abstracted from the database. Each infant's birthweight percentile for gestational age was calculated on the basis of published US references; infants below the 10th percentile were classified as SGA. The performance characteristics of SGA ICD-9-CM diagnosis code against SGA classification based on birthweight and gestational age were calculated, for all deliveries and by strata of demographic and delivery characteristics.</p>

<p><strong>RESULTS: </strong>We identified 51 292 singleton live birth deliveries. The prevalence of SGA infants calculated from birthweight and gestational age at birth was higher (13%) than the prevalence based on ICD-9-CM code (2%). Sensitivity of the SGA ICD-9-CM code was 14.2%, specificity was 99.7%, positive predictive value was 86.8%, and negative predictive value was 88.4%. Stratification by demographic and delivery characteristics yielded similar results.</p>

<p><strong>CONCLUSIONS: </strong>Identification of SGA infants using ICD-9-CM code, 656.5x, from administrative healthcare records has low sensitivity but high specificity; the accuracy did not differ across demographic and delivery characteristics. Thus, although this source of information would underestimate the prevalence of SGA, it could produce valid relative risk estimates.</p>