PURPOSE: Recent guidelines suggest the use of spirometric reference values that are race/ethnic group specific. Despite the availability of such data for Caucasian, African-American, and Mexican-American subjects from a sample of the United States population, many institutions instead rely on reference values from less diverse populations corrected with adjustment factors to approximate racial/ethnic specificity. Adjustment factors require calculation and are not as accurate as race/ethnic specific values creating the potential for missed diagnoses or unnecessary testing. We studied the impact of changing spirometric reference values from those requiring an adjustment factor for race/ethnicity to those that were race/ethnic group specific.
METHODS: We conducted a retrospective analysis comparing physician interpretation of spirometry performed in 206 patients before and 260 patients after a change in the reported reference values from those obtained from Caucasian adults (Crapo, et al, 1981) to those obtained from the National Health and Nutrition Examination Survey (NHANES) III data. Physicians were instructed to use adjustment factors when the reference set was not race/ethnic group specific. Physician interpretation of obstructive defects and restrictive patterns were recorded and compared to interpretations obtained from comparison of patient values to the lower limit of normal for NHANES III reference values.
RESULTS: Of the patients, 257 (55%) were male. The mean age was 51.4 years (range 18-91). Of the patients, 317 (68%) identified themselves as Caucasian, 92 (20%) as African-American, and 57 (12%) as Hispanic. Overall, the use of race/ethnic group specific reference values led to an increase in physician diagnostic accuracy (95.2% vs. 91.0%, p = 0.01). This was reflected more in the improvement in diagnostic accuracy for identifying restriction (96.5% vs. 90.3%, p = 0.006) than in identifying obstruction (93.9% vs. 91.8%, p = 0.38).
CONCLUSION: We conclude that the use of race/ethnic specific reference equations increase the accuracy of spirometric interpretation, particularly in the identification of a restrictive pattern.
CLINICAL IMPLICATIONS: Physicians who interpret spirometry should utilize race/ethnic specific reference values to maximize diagnostic accuracy.
DISCLOSURE: Samuel Burkett, None.