IMPACT OF USING STATED INSTEAD OF MEASURED HEIGHT UPON SCREENING SPIROMETRY

This study examined the impact of using stated height instead of measu red height on predicted normal values and clinical interpretation of s creening spirometry in an outpatient referral population. In a prospec tive fashion, we evaluated 210 patients, 20 to 89 yr of age, referred for spirometry to our pulmonary function laboratory by obtaining both stated height (HTs) and measured height (HTm). The mean difference bet ween stated and measured height progressively increased with age, from 0.80 cm (20 to 29 yr; p = 0.01) to 5.70 cm (80 to 89 yr; p < 0.001). For men and women, use of HTs instead of HTm produced a mean differenc e for all ages in computing predicted FEV(1), and FVC values of 3.9 an d 4.3%, respectively. This effect was more prominent in the older age groups (80 to 89 yr, n = 30); mean differences were 11.0% (211 ml) and 11.7% (303 ml), respectively. Use of HTs instead of HTm altered the d etection of restriction by reduced FVC in 17 patients and the detectio n of obstruction by reduced FEV(1)/FVC ratio in four patients. Use of HTs altered the clinical assessment of severity by FEV(1) in 15 of 108 (13.9%) obstructed patients and altered the assessment of severity by FVC in 11 of 32 (34.4%) restricted patients, with older patients more frequently affected than younger patients. We conclude that the use o f stated height instead of measured height in the performance of scree ning spirometry can have significant impact on the calculation of pred icted normal values. These discrepancies can potentially influence the clinical interpretation of screening spirometry, affecting the detect ion of abnormality and the assessment of severity of disease, particul arly among older patients.