To examine these hypotheses, we compared ED visit rates over the period of 2001 to 2008 for dental issues versus asthma using data from the National Hospital Ambulatory Medical Care Survey (NHAMCS); the study period was chosen because it included the most recent economic recession (2008 was the most recent data available at the time of our analyses). NHAMCS is an annual, national-probability sample survey of US hospital EDs conducted by the National Center for Health Statistics. The survey excludes federal, military, and Veterans Administration hospitals and uses multistage probability sampling methods to collect nationally representative data from US emergency departments. A patient visit is the basic sampling unit for NHAMCS. Trained interviewers, over a 4-week period on an annual basis, visit a nationally-representative sample of EDs in adult and pediatric noninstitutional hospitals (general and short-stay) and collect data.
A patient record form is completed for each visit and includes information on patient demographic characteristics; patient’s complaint; time, day of week, and mode of arrival; whether the visit was injury-related and cause of injury; categories of diagnostic tests and procedures performed; discharge diagnoses; medications prescribed; and disposition. Up to 3 reason-for-visit codes and 3 discharge diagnoses are possible for each visit. Diagnoses are coded according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM).
Methodological details of NHAMCS have been described in detail elsewhere.20,21
Use of these data were exempt from review by the institutional review board of the University of Washington.
ED visits for dental care were identified using the NHAMCS “reason for visit” variable and included: symptoms of teeth and gums (NHAMCS code: 1500.0); toothache (code: 1500.1); gum pain (code: 1500.2); and bleeding gums (code: 1500.3). Reason for visit codes were chosen over ICD-9
codes because we are particularly interested in the phenomenon of patients using the ED for a perceived dental problem. Some patients may present to the ED for multiple reasons, including both medical and dental issues; use of discharge diagnosis to identify ED dental care might introduce a bias toward individuals seeking care primarily for medical problems and incidentally reporting a nonurgent dental issue at the time of visit. Additionally, the use of ICD-9
codes for dental issues is problematic because there is limited coding for dentistry and its use by physicians is typically nonspecific and inadequate.3,22
We selected ED visits for asthma as the comparison condition because asthma affects individuals across the age spectrum, as do dental problems, and represents an ambulatory-care sensitive condition. Asthma visits were identified using the ICD-9
code of 493 (asthma). The reason-for-visit variable was not used to identify asthma exacerbation because the respiratory codes for shortness of breath, dyspnea, and wheezing are nonspecific and could also represent other cardiopulmonary diseases.
We estimated ED dental visit rates by age, gender, race/ethnicity (non-Latino White [“White”], non-Latino Black [“Black”], and Latino), US Census geographic region, and insurance status (private, Medicare, Medicaid/State Children’s Health Insurance Plan [SCHIP], uninsured). Insurance status categories were created using the “PAYTYPE” variable. NHAMCS assigned the primary expected source of payment to the “PAYTYPE” variable using a hierarchical ranking (Medicaid, Medicare, private insurance, worker’s compensation, self-payment, and no charge, in decreasing order). From 2005 to 2007, patients who were dually eligible for Medicare and Medicaid were assigned Medicaid as the primary expected source of payment. Beginning in 2008, dually eligible patients have Medicare classified as their primary expected payment source. The uninsured category was compiled from visits that were identified as “self-pay,” “no charge,” or “charity.” ED dental and asthma visit rates per 1000 people were based on the weighted number of visits (weights provided by NHAMCS) divided by estimates of the civilian, non-institutionalized US population as reported by the US Census Bureau.
To test the hypothesis that secular changes had an impact on ED dental visit rates, we compared the national unemployment rate to the ED dental visit rates over the time period studies. The most recent recession, according to the Bureau of Economic Research, occurred from December 2007 to June 2009. For simplicity and because we did not have 2009 data, we regarded 2008 as the year of the economic recession. The unemployment rate is considered a coincident indicator of the economy. Coincident economic indicators measure aggregate economic activity and thus rise and fall in concordance with fluxes in the economy.23
The national unemployment rate was derived from the Bureau of Labor Statistics using the seasonally adjusted rates reported for the civilian labor force in December of each year.24
We have presented unweighted NHAMCS visit counts, weighted national estimates, and 95% confidence intervals based on survey visit weights and standard errors provided by NHAMCS. We created population-based overall ED and dental and asthma ED visit rates for each age, race/ethnicity, and insurance-specific stratum using the national weighted ED visit estimates and dividing by the corresponding stratum-specific US Census Bureau population estimates. Relative rates were calculated by dividing each of the year- and diagnosis-specific visit rates (between and including 2002 and 2008) by their baseline rates in 2001. We assessed the change in ED visit rates over time by using weighted linear regression models fitted to estimates from all years between and including 2001 and 2008. All analyses were performed using STATA 11 (STATA Corp, College Station, TX).