Concept: Total Respiratory Morbidity (TRM) - Measuring Prevalence

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Concept Description

Last Updated: 2020-05-15

Introduction
    Total Respiratory Morbidity (TRM) is a measure of several different types of respiratory illness in the population. It includes the following conditions:

    • asthma,
    • acute bronchitis and bronchiolitis,
    • chronic bronchitis,
    • bronchitis not specified as acute or chronic,
    • emphysema, and
    • chronic airway obstruction.

    This combination of diagnoses is used to overcome problems resulting from different physicians (or specialists) using different diagnosis codes for the same underlying illness (e.g. asthma versus chronic bronchitis).

    As an indicator, TRM measures the percentage of residents diagnosed with a respiratory illness and is expressed as a percentage because each resident is defined either as having been treated for any of these diseases, or not. The crude and adjusted rates can be reported.
MCHP Algorithms for Defining Total Respiratory Morbidity (TRM)
    Over time, MCHP has used different methods to identify TRM. The majority of research uses ICD coding from administrative (Hospital Abstracts and Medical Services) data. A second method identifies TRM from different types of survey data. The two methods are described below.
1. Identifying Total Respiratory Morbidity (TRM) From Administrative Data
    TRM can be identified by ICD diagnoses codes in the Hospital Abstract data or from the Medical Services / Physician Visits) data. A standard, consistent set of diagnosis codes have been used in all research projects, depending on the years of study in the project.
    NOTE: In the Hospital Abstract data, ICD-9-CM coding is used up to March 31, 2004. From April 1, 2004 forward, ICD-10-CA coding is used. In the Medical Services data, 3-digit ICD-9-CM coding is used. For more information on the use of and changes in ICD coding in different MCHP data sets, see the International Classification of Disease (ICD) Coding in MCHP Data concept.

    TRM includes the following respiratory illnesses as defined by the corresponding International Classification of Diseases (ICD) codes:

    • Bronchitis and Bronchiolitis ** - ICD-9-CM codes: 466, 490, 491; ICD-10-CA codes: J20, J21, J40, J41, J42
    • Emphysema - ICD-9-CM code: 492; ICD-10-CA code: J43
    • Asthma - ICD-9-CM code: 493; ICD-10-CA code: J45
    • Chronic airway obstruction - ICD-9-CM code: 496; ICD-10-CA code: J44
    ** Specific types of Bronchitis and Bronchiolitis are represented by the following ICD-9-CM and ICD-10-CA codes:

    • 466, J20, J21 = acute bronchitis and bronchiolitis;
    • 490, J40 = bronchitis, not specified as acute or chronic; and
    • 491, J41, J42 = chronic bronchitis
    In the hospital and physician data, TRM is defined by one of the following conditions, using the ICD diagnosis codes listed above:

    • one or more hospitalizations with a diagnosis of TRM (using ICD-9-CM or ICD-10-CA codes within the appropriate time frame), OR
    • one or more physician visits with a diagnosis of TRM (using ICD-9-CM codes).
TRM in MCHP Research From Administrative Data
2. Identifying Total Respiratory Morbidity (TRM) From Survey Data
    In The Cost of Smoking: A Manitoba Study deliverable by Martens et al. (2015) they calculated TRM prevalence rates two ways; one using administrative data and the other using self-reported survey data. Using the administrative data, the weighted crude prevalence of TRM was calculated for survey respondents aged 12 and older in year before their survey date. TRM was defined by one of the following conditions:

    • one or more hospitalizations with a diagnosis of asthma, chronic or acute bronchitis, emphysema, or chronic airway obstruction: ICD-9-CM codes 466, 490, 491, 492, 493, or 496; ICD-10-CA codes J20, J21, J40–J45 (these are the same codes listed above in section 1); or
    • one or more physician visits with a diagnosis of asthma, chronic or acute bronchitis, emphysema, or chronic airway obstruction (ICD-9-CM codes as above).

    Using the survey data, questions about respiratory disease were asked in the National Population Health Survey (NPHS) and all waves of the Canadian Community Health Survey (CCHS) except CCHS 2.2. Respondents were asked a series of questions that varied slightly across surveys, but most respondents were asked questions such as, "Do you have asthma?", "Do you have chronic bronchitis?" and "Do you have emphysema?" Possible responses include "yes", "no", or "don't know". The weighted crude self-reported prevalence of TRM was calculated for survey respondents aged 12 and older as the percentage of respondents who answered "yes" out of all respondents who gave a valid answer. Respondents who answered "don't know" or those with missing or invalid data were excluded from the prevalence calculation.

    For more information, Table 4.8 Chronic Diseases of Estimated-Population-Based Sample* at Time of Survey by Smoking Status Categories lists the prevalence rates of TRM from survey (self-reported) and administrative data found in this report.

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References 

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