Medicaid Claims Data

Uses for Asthma Surveillance

Several questions can be addressed statewide using Medicaid Data:
Q What is the prevalence of health services for asthma among Medicaid beneficiaries?
Q What is the prevalence of “persistent” asthma among Medicaid beneficiaries?
Q What is the amount of Medicaid dollars spent for asthma medications and asthma-related services per Medicaid beneficiary?
Q What percentage of Medicaid beneficiaries with asthma are receiving appropriate long-term control medications?
Q What are the different asthma medications that Medicaid beneficiaries are receiving?
Q What are the annual rates of ED visits, hospitalizations, and office visits for asthma among Medicaid beneficiaries?
Q How does the prevalence of health services for asthma and “persistent” asthma vary by age, sex, race/ethnicity, and county among Medicaid recipients?

History of Medicaid Data Collection and suggested Asthma Case Definitions

History. Under Title XIX of the Social Security Act of 1965, Medicaid was established as an entitlement program to provide medical assistance for certain low-incomes or disabled individuals. The program is administered by the States and is funded by the State and Federal Government.

The States configure their own Medicaid programs. They combine the required federal eligibility criteria, benefits, and provider payment rates with the State options. According to Federal mandate, the States collect person-level eligibility and health service claims records about each enrollee. These data are held in electronic files that are used for program administration purposes, for research, surveillance, and statistical reports, and to fill other program-related needs.

Providers submit claims to the state Medicaid Management Information System (MMIS). MMIS files include detailed data for program administration such as names and addresses. From the MMIS files, the states construct quarterly eligibility and claim files for submission to the Center for Medicaid and Medicare Services (CMS); these are called Medicaid Statistical Information System (MSIS) files. The eligibility file includes everyone with at least one month of enrollment in Medicaid during that quarter. The claims are organized into four separate categories: inpatient acute hospital care; long-term care; medications; and all other ambulatory claims. The MSIS data dictionary is available at iconexternal icon. Users can obtain the MSIS files from a state or from CMS. From the MSIS quarterly files, CMS constructs Medicaid Analytic Extract (MAX) files for use in research, surveillance, and statistical reporting, and support the development of national statistics and cross-state comparisons (from 1996 – 1998 the MAS files were called “State Medicaid Research Files,” or SMRFs).

Because Medicaid provides medical assistance to low-income and disabled individuals, any estimation of the burden of asthma that is undertaken using this data will typically reflect low socioeconomic status populations. Additional information and resources pertaining to the Medicaid program can be found at icon.

Asthma Case Definitions. Data elements typically included in Medicaid data include age, sex, race and county of residence. Data are available on claims for asthma-related hospital acute care, ambulatory care (office visits, ED visits), and medication dispensation. There are several standard asthma-related case definitions that can be used.

  1. The Council of State and Territorial Epidemiologists (CSTE) ( iconexternal icon) has jointly developed a standardized case classification to identify probably and possible cases of asthma in hospital discharge data. This classification may be applicable also to Medicaid data for claims for inpatient and ambulatory visits.
    • Confirmed Case: There is no confirmed case classification for Medicaid data.
    • Probable Case: Inpatient or ambulatory Medicaid claims listing asthma (any ICD-9-CM Code 493 and ICD-10-CM Code J45) as the primary discharge diagnosis.
    • Possible Case: Inpatient or ambulatory Medicaid claims listing asthma (any ICD-9-CM Code 493 and ICD-10-CM Code J45) as a secondary discharge diagnosis or a primary discharge diagnosis of acute bronchitis and bronchiolitis (ICD-9-CM Code 466; ICD-10-CM Code J20-J21) in children younger than 12 years, or chronic bronchitis (ICD-9-CM Codes: 491.20 and 491.21; ICD-10-CM Codes J40-J41) in children younger than 12 years.
  2. The National Committee for Quality Assurance (NCQA) also has developed standards to define persons with persistent asthma1. Persistent asthma can be defined as:
    • Four or more prescription medications filled for the treatment of asthma in a year, OR
    • One or more inpatient hospital stays with a primary diagnosis of asthma in a year, OR
    • One or more ED visits with a primary diagnosis of asthma in a year, OR
    • Four or more ambulatory visits with asthma listed anywhere as one of the diagnoses and two (2) or more claims for a prescription drug filled for the treatment of asthma within 1 year.

    The NCQA has developed a list of Common Procedural Terminology codes and Uniform Billing-92 (UB 92) revenue codes that are designed to more sensitively capture inpatient and ambulatory prepaid managed care encounter claims. This is because Medicaid data are based on paid claims (fee-for-service claims, per-service managed care claims, primary care case management fees, etc.) and rather than encounters. Persons can obtain more information about this at http://www.ncqa.orgexternal icon.

  3. For the assessment of appropriate medication use, HEDIS has set a standard for appropriate prescription drug treatment that requires a person with asthma to have received any of the drugs identified by the NCQA as a primary therapy for the long-term treatment and control of asthma.2 The NCQA puts out annual lists of National Drug Codes (NDCs, icon, scroll down and click accept to enter the site) that indicate the drugs classified as long-term asthma controllers as well as NDCs of current long-term and short-term asthma medications. These drug codes provide a standard that may be used when classifying an asthma “case” based on medication use, or when calculating the proportion of persons with asthma who are on long-term control medications. However, any asthma case definition should identify the proportion of all asthma cases that were defined through diagnosis, medication prescription, or both.

Source of Data (How to Access the Data)

Medicaid data are available from the state Medicaid program or from the Centers for Medicare and Medicaid Services (CMS). In many states the Medicaid program is housed within the Department of Health (but often is separate from public health activities). In other states the Medicaid program forms its own agency. In addition, there may be variability between states in the number and type of patient, provider, and hospital identifiers that are included in the shared data sets. Those who are interested in acquiring and analyzing state Medicaid data for asthma surveillance purposes should contact their state Medicaid director or CMS. The contact information of the Medicaid director for each state or territory is available at icon . Information about obtaining CMS Medicaid files can be found at http://www.resdac.umn.eduexternal icon (888-9-RESDAC or Statistical inquiries pertaining to Medicaid data also can be directed to CMS at 410-786-0165 or

Preparation of Data and Standard Methods for Rate Calculations

Selected Important Differences between the State and CMS MSIS files and the CMS MAX files

  • In the MAX files, the claims are ordered by date of service; the claims are ordered by date of payment in the MSIS files. On average, most claims are paid within nine months of the service date. This means that researchers who use these files will need to review three quarters to….

In order to enhance the comparability of asthma-related morbidity estimates between states, the following steps outline a standard process for preparing Medicaid data for asthma surveillance purposes.

  • Claims for persons with other sources of insurance in addition to Medicaid will need to be removed from the data set. Specifically we encourage that Medicaid enrollees with additional insurance (including Medicare) be excluded from analyses because their encounters will not be submitted for payment to the Medicaid system. Similarly, persons in capitated managed care programs that do not provide encounter-level data to the states also need to be excluded.
  • Claims for persons aged 65 and older also will need to be removed from the data set due to the potential misclassification of asthma with other respiratory diseases, and due to the impact of Medicare penetration in the older population.
  • The date of any asthma encounter is identified by the service date of the claim, not the date on which the claim was paid.
  • Identify the paid claims for ambulatory, inpatient, and ED services and medication claims data in both Medicaid fee-for-service and Medicaid managed care systems. As data are collected to pay claims, multiple records for a single claim accumulate in Medicaid data. Only “fully adjusted” claims should be selected to avoid counting the same claim more than once.
  • In the Medicaid system multiple claims may legitimately exist for a single service. For example, a single asthma hospitalization may result in both hospital claims and physician claims. In order to count each asthma service or event only once, fully adjusted claims with a diagnosis of asthma or for asthma medications must be combined and unduplicated using the ID number and beginning date of service.
  • Medicaid claims data are “encounter data.” This means that raw Medicaid files may include many claims for the same event. As a result, when asthma prevalence rates are calculated the fully-adjusted paid claims with a diagnosis of asthma and/or paid drug claims pertaining to asthma must be combined and unduplicated using the Medicaid ID number and beginning date of service. This is done so that each person with asthma is only counted once when developing a prevalence estimate, and so that an event (such as a hospitalization) is only counted once in analyses of asthma-related use.
  • The denominator for any rate should be the number of persons continuously enrolled in the state Medicaid program during each year in the time period covered by the rate. We suggest that “continuous enrollment” be defined as enrollment of a full year with no more than a one month gap in enrollment (i.e., 11 or more months of enrollment per year). If calculating the HEDIS asthma measure, stricter criteria for continuous enrollment is needed (i.e., 11 or more months of enrollment in the year prior to measurement year and in the measurement year).

In summary, it is important to be sure that the criteria used to determine inclusion in the numerator is as similar as possible as the criteria used for assignment in the denominator. Following these steps will produce estimates of asthma morbidity among continuously enrolled Medicaid recipients under age 65 with no other insurance. This process will also increase the comparability of Medicaid-derived asthma morbidity estimates across states. However, it remains important to remember that state-based differences in Medicaid eligibility criteria and programming may continue to produce state-to-state differences in the populations represented by Medicaid data.

Analysis Standards

The NATC Surveillance module includes a discussion of standard demographic breakdowns for use when analyzing asthma surveillance data. The applicability of these breakdowns to state Medicaid data is summarized below.

  • Age Categories: Rates can be calculated by age for five-year age intervals for groups between the ages of 0 and 24 (e.g., 0-4, 5-9, etc), and 10-year age intervals for groups aged 25 to 55 (e.g., 25-34, 35-44, 45-54, 55-64). Rates obtained for persons over age 65 may be due to potential misclassification with other respiratory diseases, and because of the impact of Medicare penetration in the older population.
  • Sex Categories: Rates can be calculated separately for “male” and “female” categories.
  • Race Categories: “White,” “Black or African American,” “American Indian or Alaska Native,” “Asian or Pacific Islander,” “Hispanic or Latino,” “Native Hawaiian or other Pacific Islander” and “Other” are typically mutually exclusive categories in Medicaid data and rates can be calculated separately for each of these categories.
  • Time Trends: Rates should be calculated by year if possible. Rates also can be calculated by month, day of week, and time of day. However, when calculating trends in Medicaid data, care should be taken to determine that no changes in state eligibility criteria have occurred during the time period in questions. Such changes could influence the number of asthma cases “captured” and the type of population that is represented by the state Medicaid data.
  • Geographic Categories: Rates can be calculated at the state, county, and zip code levels if the cell sizes permit. Age standardized rates will be needed to compare geographic units.

NOTE: Small sample size can result in release or inferred release of confidential or sensitive information and can also affect reliability of rates. Please consider collapsing years or demographic groups, presenting confidence intervals, and/or suppressing rates and counts if sample size of the numerator or denominator is inadequate. In some cases, an aggregation of categories of data may be necessary to achieve the relative standard error of 30% that has been suggested to produce reliable rates ( icon). For example, if the event count is <20 in any particular year, we recommend combining years to achieve numerators > 20, and/or estimating trends based on 3-year rolling averages (e.g., calculate a single rate for 1978-1980, then 1979-1981, etc). To protect patient confidentiality, CMS requires that “data must not be beneficiary-specific and must be aggregated to a level where no data cells have 10 or fewer beneficiaries.”2

Anticipated Questions and Answers

Q Do Medicaid asthma claims data accurately reflect the overall burdens of asthma?
A No, this is because Medicaid claims data are only representative of persons in a state who meet state Medicaid eligibility criteria. This may vary from state to state. Typically these persons are of younger age and lower socio-economic status than the overall state population. In addition, Medicaid data may be incomplete because these data are based on paid claims, not all encounters.

Q What are the main strengths of Medicaid claims data for the purposes of asthma surveillance?
A In the absence of local surveys of the burden of asthma, Medicaid claims data provide important information about the cost of asthma, the medications being prescribed for asthma, and the severity of asthma for low income (and often high risk) populations. In addition, some states may not have access to state hospitalization data, or hospitalization data from a local hospital administration. In these cases Medicaid data may be one of the only sources of hospital encounter data.

Q Can residents form other states also be included in Medicaid claims data?
A Yes, these data need to be excluded when calculating rates only for state residents.

Q How can the “cost of asthma” be calculated using Medicaid claims data?
A The average amount paid by Medicaid for each asthma related encounter can be calculated by totaling the dollar value of claims paid for asthma-related prescriptions and treatment services, then dividing this number by the number of asthma related medical encounters during a given time period. If the data have been unduplicated using the Medicaid ID number, the average cost per asthma patient, per year can also be calculated.

Q Will following the procedures in the fact sheet produce asthma surveillance estimates that are comparable across states?
A Following the process outlined in this fact sheet will increase the comparability of Medicaid-derived asthma morbidity estimates across the states. However, it remains important to remember that state-based differences in Medicaid eligibility criteria and programming may continue to produce state-to-state differences in the populations represented by Medicaid data.

State and Federal Contacts and Resources for Medicaid Data

Centers for Disease Control and Prevention (CDC)
National Center for Environmental Health
Asthma and Community Health Branch
General Number: (770) 488-3700

Some states and cities that have produced asthma publications using Medicaid claims data: California, Illinois, Maine, Michigan, Nebraska, New York, North Carolina, and Oregon (see below for contact information for these States’ asthma contact persons).
Current contact information for all state asthma contacts:

Centers for Medicare and Medicaid Services
Research Data Assistance Center (RESDAC)

www.resdac.umn.eduexternal icon
General Number: 888-973-7322


  1. National Committee for Quality Assurance. Use of appropriate medications for people with asthma. HEDIS 2014 technical specifications. Vol 2.
  2. Medicare Fee-For Service Provider Utilization & Payment Data Physician and Other Supplier Public Use File: A Methodological Overview,” Prepared by: The Centers for Medicare and Medicaid Services, Office of Information Products and Data Analytics, April 7, 2014. Available at iconexternal icon
Page last reviewed: May 17, 2019