PURPOSE: Bronchiolitis obliterans syndrome (BOS) is a rare, deadly manifestation of chronic graft-versus-host disease (cGVHD) following HSCT. Because of the morbidity associated with biopsy, clinical criteria are proposed for diagnosis. This definition includes pulmonary function test (PFT) parameters: FEV1<75% predicted, FEV1/VC<0.7, and RV or RV/TLC>120% predicted (JAMA2009;302:306). This BOS diagnosis may depend on the reference equation used. Although NHANES III is the recommended standard, other equations are commonly used. Purpose: To determine the effect of using NHANES III reference vs. older equations, on the number of patients clinically diagnosed with BOS.
METHODS: 166 consecutive standardized PFT interpretations using both NHANES III and our institution’ s previous reference equations (Morris/Goldman/Bates-MGB) were compared with respect to FEV1% predicted and FEV1/FVC. The resulting 4 classification groups were assessed for degree of agreement using McNemar’ s exact test for paired categorical data. Mortality was determined using clinical records and SSDI.
RESULTS: Assessing only FEV1% predicted, 11% (18/166) of patients were classified as normal by MGB(>75%) and abnormal by NHANES III(<75%) while 0/166 were classified as abnormal by MGB(>75%) and normal by NHANES III(<75%) (p< 0.0001). Evaluating only FEV1/FVC ratios, 95% (157/166) were concordant by confidence interval. One ratio was abnormal by MGB, but normal by NHANES III, and therefore excluded from a diagnosis of BOS using NHANES III. The discordant ratios were divided evenly between > 0.7 (n=4) and < 0.7 (n=5) (p=1.00). Using the proposed amended PFT definition of BOS and the NHANES III classification, 6 additional patients (17%) would have been diagnosed with BOS, and one would have been removed from the BOS cohort. For 33/35 BOS patients with > 1 year follow-up, this changed mortality rates from 6/24 (25%) (MBG) to 4/22 (18%) (NHANES III) for mild/moderate disease; severe BOS (FEV1<35%) mortality was 6/7 (86%, MGB) and 8/9 (89%, NHANES III).
CONCLUSION: Using NHANES III reference equations significantly increased the number of subjects in our cohort with a clinical diagnosis of BOS.
CLINICAL IMPLICATIONS: These data may have implications for incidence and survival prediction.
DISCLOSURE: Kirsten Williams, No Financial Disclosure Information; No Product/Research Disclosure Information