Elsevier

Heart & Lung

Volume 31, Issue 4, July–August 2002, Pages 262-270
Heart & Lung

Issues in Cardiovascular Nursing
Validity and reliability of the NYHA classes for measuring research outcomes in patients with cardiac disease*

https://doi.org/10.1067/mhl.2002.124554Get rights and content

Abstract

The New York Heart Association (NYHA) functional classification system was developed to help physicians in clinical practice evaluate the effect of cardiac symptoms on a patient's daily activities. Over time, the role of the NYHA classification system has expanded, and it is now frequently used in clinical research. This review of the literature was undertaken to explore whether the NYHA classes have sufficient validity and reliability to serve as a functional outcome measure in research studies. After exploring its strengths and limitations, we conclude that the NYHA classes are a valid measure of functional status, a concept that is distinct from functional capacity and functional performance. The reproducibility of the NYHA functional classification system has not been established in the literature. Researchers are urged to report the methods for determining NYHA class, the training of raters, and the intra-rater or inter-rater reliability in studies that have multiple raters or measurements. Until the reliability of the NYHA functional classification system is determined, it is prudent to refrain from using the NYHA classes as the sole outcome measure of change in function in research studies of cardiac patients. (Heart Lung® 2002;31:262-70.)

Section snippets

Development of the NYHA functional classification system

When the NYHA functional classification system was originally developed in 1928, it represented a major advance in the assessment of CVD that allowed physicians to identify and communicate gross changes in illness severity. The wording that describes the NYHA classes in the current version of the NYHA classification system,13 shown in Table I, uses descriptions of the classes developed by a criteria committee in 1964.The NYHA system was designed for clinical assessment of patients by physicians

Concepts of function in cardiac patients

Measures of function in research studies must be conceptually clear to differentiate the various types of function that may be affected by other variables. Functional capacity is a concept that represents the maximum physiologic function of which a person is capable.16 A related concept, functional performance, represents the amount of function that a person chooses to actually perform (ie, a person may be capable of a high level of functional capacity but may perform at a lower level for a

Essential characteristics of measurement instruments

Validity and reliability are essential characteristics of any measurement instrument. An instrument that is valid is one that precisely measures the concept that it is intended to measure. It should correlate with other instruments that measure the same concept and have low or moderate correlation with measures of related, but different, concepts. To select a valid research measure, it is essential to clarify the outcome concept that appropriately answers the research question and to choose a

Validity of the NYHA functional classification system

Because functional capacity, functional performance, and functional status are related but unique concepts, a moderate correlation would be expected between measures of these concepts. Studies comparing the NYHA functional classifications (functional status) to measures of functional performance and functional capacity have reported low to moderate correlations between measures, supporting the validity of the NYHA classes as a measure of functional status but not of performance or capacity.

In

Reliability of the NYHA functional classification system

If the NYHA functional classification system is used in an intervention study as a measure of change in functional status over time, multiple evaluations of NYHA class by a rater must be reliable. Further, if multiple raters evaluate NYHA class, inter-rater reliability should be assessed and reported. Yet, intra-rater and inter-rater reliability of the NYHA classes have rarely been reported in the research.

Appropriate classification relies on the judgment, observations, and interpretation of

Discussion and recommendations

The NYHA functional classification system is widely used by health care providers as a clinical measure to distinguish cardiac patients who are disabled by cardiac symptoms from those who are less ill. It is not surprising that the NYHA classes have stood the test of time in clinical situations since the classifications are simple to use; provide a rough estimate of the impact of illness; and correlate to some degree with other measures of function, such as VO2max, the SAS, and the 6-minute

Acknowledgements

The authors gratefully acknowledge Thomas A. Gillespie, MD, and Derek Exner, MD, for their reviews of a prior version of this manuscript.

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    Reprint requests: Jill A. Bennett, UCSF School of Nursing, San Francisco, CA 94143-0610.

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