Collection of Information about Prescription Medications

Overview

Data regarding prescription drugs were obtained through the household questionnaire and a pharmacy component survey. During each round of the MEPS-HC, all respondents were asked to supply the name of any prescribed medication they or their family members purchased or otherwise obtained during that round. For each medication and in each round, the following information was collected: whether any free samples of the medication were received; the name(s) of any health conditions the medication was prescribed for; the number of times the prescription drug was obtained or purchased; the year, month, and day on which the person first used the medication; and a list of the names, addresses, and types of pharmacies that filled the household's prescriptions. Note that not all of this information was made available in the public-use files. Refer to the RX medicines drop-down menu for a listing of prescribed medicine variables available through IPUMS MEPS.

During the Household Component, respondents were also asked if they send in claim forms for their prescriptions (self-filers) or if their pharmacy providers do this automatically for them at the point of purchase (non-self-filers). For non-self-filers, charge and payment information was collected in the pharmacy component survey, unless the purchase was an insulin or diabetic supply/equipment event. However, charge and payment information was collected for self-filers in the household questionnaire, because payments by private third party payers for self-filers' purchases would not be available from the pharmacy component. Uninsured persons were treated as those whose pharmacies filed their prescription claims at the point of purchase. Persons who said they did not know if they sent in their own prescription claim forms were treated as those who did send in their own prescription claim forms.

When diabetic supplies, such as syringes and insulin, were reported in the other medical supply section of the MEPS-HC questionnaire as having been obtained during the round, the interviewer was directed to collect information on these items in the prescription drug section of MEPS. Charge and payment information was asked for these events.

The Pharmacy Component Survey

Pharmacy providers identified by the household were contacted by telephone in the pharmacy component if permission to release their pharmacy records was obtained in writing from the person with the prescription. The signed permission forms were provided to the various establishments prior to making any requests for information. Each establishment was informed of all persons participating in the survey that had prescriptions filled there during the year in question and a computerized printout containing information about these prescriptions was sought. For each medication listed, the following information was requested: date filled, national drug code (NDC), medication name, strength of medicine (amount and unit), quantity (package size and amount dispensed), and payments by source.

Prescribed Medicines File

The general approach to preparing the household prescription data for the Prescribed Medicines File was to utilize the Pharmacy Component prescription data to assign expenditure values to the household drug mentions. The Pharmacy Component (PC) is a subcomponent of the Medical Provider Component (MPC) and detailed drug information is collected, including National Drug Code (NDC) and medicine name, date filled, and sources and amounts of payment. The MPC (and PC) are not designed to yield national estimates, but rather are primarily used as an imputation source to supplement/replace household-reported expenditure information.

Editing and Imputation of the Pharmacy Expenditure Information

General Information

For events for which charge and payment data were collected from the household in the Household Component (HC), information on payment sources was retained to the extent that these data were reported. For those with PC data, a matching program was adopted to link pharmacy component drugs and the corresponding drug information to household drug mentions. To improve the quality of these matches, all drugs on the household and pharmacy files were coded based on the medication names provided by the household and pharmacy, and when available, the NDC provided in the PC. Considerable editing was done prior to the matching to correct data inconsistencies in both data sets, fill in missing data, and correct outliers on the pharmacy file.

Drug price per unit outliers were analyzed by on the pharmacy file by first identifying the average wholesale unit price (AWUP) of the drug by linkage through the NDC to a proprietary database. In general, prescription drug unit prices were deemed to be outliers by comparing unit prices reported in the pharmacy database to the AWUP and were edited, as necessary. Beginning with the 2007 data, the rules used to identify outlier prices for prescriptions in the pharmacy component changed. New outlier thresholds were established based on the distribution of the ratio of retail unit prices relative to the AWUP in the 2007 MarketScan Outpatient Pharmaceutical Claims database.

Confidentiality

Users should note that some of the information on the prescribed medicines records has been masked in cases where the information poses a confidentiality risk. Prescription medications can pose a confidentiality risk for several reasons. Examples include orphan drugs, drugs that are estimated to be used by fewer than 200,000 people, or drug names that provide identifying information about the pharmacy or respondent. An orphan drug is a drug that treats a rare disease or condition but has been discontinued because there is little or no economic incentive to continue development or production. See Rare Diseases at the FDA for more information about how these drugs are designated and the effort to financially support their development and production under the Orphan Drug Act. See the variable descriptions for more detailed information about how cases that pose a confidentiality risk are handled in the data.

Missing Data

Information obtained from the pharmacy component and other proprietary databases is not always complete, leading to instances of missing data. The source provider chose to leave these data missing because this information can be obtained via the National Drug Code (NDC). Users can use the NDC value to fill in any missing information needed for their analysis. For more information about how missing data are handled by IPUMS, see MEPS missing data codes.

Rounding

Users should note that there is a slight difference in how rounding is handled between the person-level and prescribed medicines records. Person-level records are rounded to the nearest dollar, and prescribed medicines records are rounded to the nearest penny. Thus, using the prescribed medicines records to calculate person-level summary variables will result in values that are slightly different from the summary variables available on the person-level records. Additionally due to rounding, the number of persons with expenditures for a given source of payment on the prescribed medicines record may vary from the number of persons with expenditures for a given source of payment on the person-level record.

Round 3 Processing

Interview Round 3, which spans the end of the first calendar year and the beginning of the second calendar year required AHRQ to make decisions about whether drug fills reported in the Round 3 interview should be attributed to the first or second calendar year. Drug fills reported during the Round 3 interview were attributed based on several critera, including the number of times the respondent said the drug was purchased in the respective year, the year the person started taking the drug, the length of the person's round, the dates of the person's round, and the number of fills of that drug for that person in the round.