The “BHDE index,” a newly created diagnostic index for predicting outcomes of chronic obstructive pulmonary disease (COPD), has the same prediction capacity as the BODE index and is easier to administer — because the BHDE uses post-exercise heart rate recovery (HRR) data where the BODE index uses spirometry data. These are among study findings published in BMC Pulmonary Medicine.

The BODE index is a multidimensional scoring system for predicting COPD outcomes that takes into account body-mass index (B), airflow obstruction (O), dyspnea (D), and exercise (E).  The airflow obstruction measurement relies on spirometry, which was a cause for concern during the COVID-19 pandemic due to the potential for aerosolized biohazards from spirometry. In light of that concern, and in recognition of the link between cardiovascular dysfunction and poor clinical outcomes, investigators sought to test a modification to the BODE index that replaced spirometry data (O) with data on account heart rate recovery (H). Given this modification to the BODE index, researchers called their index the BHDE.

The researchers defined heart rate recovery as the difference in heart rate immediately after vs 1-minute after the 6-minute walk test. Abnormal heart rate was defined as less than 11 beats per minute (bpm).

The BHDE index was developed and validated through a retrospective observational study of 447 patients with COPD from the National Taiwan University Hospital (10% women; median body mass index, 23.5).  The researchers created the model from January 2019 to December 2019 using a derivation cohort (n=187) and validated the model between January 2020 and December 2020 using validation cohort (n=260).  Notably, the validation cohort had significantly fewer patients who actively smoked, compared with the derivation cohort.

The BHDE-index is a good and easy-to-perform prediction model for the risk of severe acute exacerbation and 1-year mortality in COPD wherever spirometry results are unavailable.

All patients had spirometry-confirmed COPD (forced expiratory volume in the first second [FEV1] percent predicted, 66%; resting heart rate, 82 bpm; 6-minute walk distance, 373 m), and all were enrolled in the Taiwan nationwide COPD pay-for-performance program, which provided participants with comprehensive pharmacologic and nonpharmacologic therapies. Patients received pulmonary rehabilitation evaluation at enrollment and were encouraged to do regular follow-up every 3 months.

The researchers found patients with abnormal HRR (n=236 from the combined cohorts) vs those with normal HRR (n=211) had a higher frequency of severe acute exacerbation in the previous year (29 vs 10), shorter 6-minute walk distance (331 m vs 420 m), faster resting heart rate (85 vs 78 bpm), more severe airway symptoms and airway obstruction (FEV1 predicted, 61 vs 71), and were older (median age, 73 vs 70 years).

Similar predictive performance for 1-year severe COPD exacerbation between the BHDE index vs the BODE index was noted in the derivation and validation groups (area under the receiver operating characteristic curve [AUROC], 0.76 vs 0.75; P =.369) and (AUROC, 0.74 vs 0.79; P =.05), respectively.

Similar predictive performance between the BHDE index vs the BODE index for 1-year mortality was found in both derivation and validation cohorts (AUROC, 0.80 vs 0.77; P =.564) and (AUROC, 0.76 vs 0.70; P =.234), respectively.

The BHDE index functioned as an independent predictor of annual severe COPD exacerbation in both cohorts in univariate and multivariate analyses.

Study limitations include the potential for incomplete records of acute exacerbations and an overwhelming predominance of men, which limited generalizability.

“The BHDE-index is a good and easy-to-perform prediction model for the risk of severe acute exacerbation and 1-year mortality in COPD wherever spirometry results are unavailable,” study authors concluded. “Post 6-min walk HRR measurement can be a potential outcome predictor for severe acute exacerbation and mortality of COPD,” the researchers added. 

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