About COPD Data

about copd

Tracking Chronic Obstructive Pulmonary Disease (COPD) involves collecting data about the number of hospital or emergency room visits due to COPD.

This page provides general information about COPD data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.

Information on this page:

What do these data tell us?
How can we use these data?
What can these data not tell us?
What are the sources of the data?
What time period of data is available?
How are COPD hospitalizations and emergency department visits identified?
What is the difference between a number, rate, and age-adjusted rate? How would I use them?
What are the limitations of the data?
Where can I find more technical information about the data?

What do these data tell us?

The numbers and rates of COPD hospitalizations and emergency department visits in Iowa by year, age group and gender.
If a COPD measure is going up or down over time.
If a segment of a population is at higher risk for hospitalization or a visit to the emergency department due to COPD.

How can we use these data?

To inform the public about COPD hospitalizations and emergency department visits.
For program planning and evaluation by state and local partners.

What can these data not tell us?

What causes COPD, or what leads to COPD hospitalizations and emergency department visits.
The total burden of COPD in a population.
The number of people who are hospitalized or who visited the emergency department due to COPD. Because personal identifiers are removed from the hospital discharge data before analysis, individuals who have multiple hospitalizations or emergency department visits cannot be identified.

What are the sources of the data?

Hospitalization and emergency department data are collected by the Iowa Hospital Association on behalf of IDPH in accordance with Iowa Code section 135.166.
Bridged-race population estimates from the National Center for Health Statistics and US Census. Data from 2000 to 2009 are based on intercensal population estimates and 2010-most current year are based on the postcensal population estimates.

What time period of data is available?

The Iowa Public Health Tracking portal displays hospitalization data from the year 2000 through the most recent year of data available.
The Iowa Public Health Tracking portal displays Emergency Department visit data from the year 2003 through the most recent year of data available.
There is usually a two-year lag period before hospitalization and emergency department visit data are available.

How are COPD hospitalizations and emergency department visits identified?

Hospitalizations:

Hospitalizations are defined as Iowa residents who are discharged from a hospital in Iowa.
Emergency Department visits are defined as Iowa residents who are treated and released or subsequently admitted to a facility in Iowa.
COPD hospitalizations have a primary discharge diagnosis of COPD.
COPD emergency department visits have COPD as the first-listed diagnosis.
COPD is defined as the International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) codes that begin with 490, 491, 492 or 496. Also includes primary diagnosis of 493.2 when a code that begins with 490, 491, 492 or 496 is present in any of the secondary diagnosis fields.
COPD is defined as the International Classification of Disease 10th Revision, Clinical Modification (ICD-10-CM) codes that begin with J40 - J44.
Because COPD is a disease of adults, only ages 25 and older are included in summary rates for the population.

What is the difference between a number, rate, and age-adjusted rate? How would I use them?

Number:

If you want to understand the magnitude or how big the overall burden is, then use the number.
The number indicates the total number of hospitalizations or emergency department visits due to COPD, but not the number of unique individuals hospitalized or who visited the emergency department.
To protect an individual's privacy, counts of 5 or less are suppressed.

Crude Rate:

If you want to understand the probability or what is the underlying risk in a population, then use a rate.
In our analysis a rate is calculated using a numerator, the number of COPD hospitalizations during a period of time, divided by a denominator, the number of people in a population during the same period of time. This fraction is then multiplied by 10,000 to provide a more recognizable value.
To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

Age-adjusted rate:

Age-adjusted rates are useful when comparing the rates of two population groups that have different age distributions.
A weighted average, called the direct method, is used to adjust for age in this analysis. Age specific rates in a given population are adjusted to the age distribution in a standard population by applying a weight. The U.S. 2000 Standard population is used as the basis for weight calculations.
To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

Age-specific rate:

A rate of an event (such as disease or death) measured within a particular age group. It is similar to a crude rate but is calculated within an age group (e.g. an age-specific rate of COPD hospitalizations in adults 35-44 years of age).
To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

What are the limitations of the data?

Multiple hospitalizations or emergency department visits by the same patient cannot be identified, and are not excluded.
It cannot tell us what causes COPD, or what leads to seeking medical care for COPD.
These data are not appropriate for estimating the total burden of COPD.
These measures use hospital admission dates while other public health programs use the hospital discharge dates to count COPD cases. This may cause a difference in COPD rates between the Tracking Network and other public health websites.
Iowa residents discharged from hospitals in surrounding states are not included, so hospitalization and emergency department visit rates for counties in which residents are likely to receive care in a surrounding state may be underestimated. Rates for counties in which residents are likely to visit hospitals that do not submit data to the Iowa Hospital Association (e.g., Veteran's Administration, Indian Health Services hospitals, and institutionalized populations) may also be artificially low.
There is usually a two-year lag period before hospitalization and emergency department visit data are available.

Where can I find more technical information about the data?

More detailed documentation of the COPD data can be found in the following documents:

Indicator Profiles

Emergency Department Visits for COPD pdf
Hospitalizations for COPD pdf

Descriptive Metadata

Emergency Department Visits for COPD pdf
Hospitalizations for COPD pdf