GOLD Versus STAR: Comparing 2 COPD Severity Classification Systems

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification system is a superior chronic obstructive pulmonary disease (COPD) severity assessment than the STaging of Airflow obstruction by Ratio (STAR) classification, according to new findings, based on all-cause mortality and COPD-specific health status.¹

These results were the conclusion of a recent study that compared the observed staging of COPD through the STAR and GOLD disease severity classifications in clinical settings. The research was led by Koichi Nishimura, a visiting researcher at the National Center for Geriatrics and Gerontology in Obu, Japan.

Nishimura and colleagues noted that COPD severity measurement has remained a well-known struggle for clinicians, with an assessment of the ratio of forced expiratory volume in a single second (FEV1) to forced vital capacity (FVC) mentioned as part of the GOLD classification. Nevertheless, disagreements remain on measuring COPD severity.

“Since the authors are in the process of conducting a cohort study summary of our own institution, we attempted to compare STAR and GOLD using data obtained from our clinical practice since it is important to examine whether their hypotheses work for populations with very different backgrounds,” Nishimura and colleagues wrote. “The aim of the present study is to compare the staging of COPD using the GOLD and STAR classifications in clinical practice in Japan.”^2,3

Background and Methods

In the period between 2013 - 2023, the Respiratory Medicine Outpatient Clinic at the aforementioned Center for Geriatrics and Gerontology carried out a longitudinal study. It would involve the inclusion of 141 subjects aged 50 and above with COPD, a post-bronchodilator forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) ratio which was under 0.7, and a history of smoking lasting at least 10 pack-years.

Subjects would also be included with normal results on their chest X-rays, a lack of active pulmonary diseases or any unmanaged comorbidities, and treatment for the previous 4 weeks which was stable. Individuals known to have recent asthma histories or any reported COPD exacerbations were excluded from the research.

The subjects involved in the research team’s analysis were given biannual assessments following at least 6 total months of prior outpatient care for the purposes of stability. Data from the point of baseline in 2015 were implemented, integrating the Kihon Checklist for assessment of subjects’ frailty.

Up until January 2023, the investigators gathered their data, having the spirometry performed after a 12-hour bronchodilator abstention with a CHESTAC-8800 spirometer. The study subjects were classified in terms of their severity through the use of the GOLD and STAR classifications based on FEV1 and FVC.

There were 4 specific severity grades among participants that had an FEV1/FVC ratio <0.70, with each of them being STAR 1 ≥0.60 to <0.70, STAR 2 ≥0.50 to <0.60, STAR 3 ≥0.40 to <0.50, and STAR 4 <0.40. In the GOLD classification system, individuals with FEV1 ≥ 80% predicted were placed in the GOLD 1 group, those with 50% ≤ FEV1 < 80% predicted in GOLD 2, those with 30% ≤ FEV1 < 50% predicted in GOLD 3, and those with FEV1 < 30% predicted labeled as GOLD 4.

The participants’ health status was evaluated through the use of the Japanese versions of the SGRQ and CAT questionnaires. The research team assessed death rates and compared severity classification systems.

Findings

The investigators assessed the alignment between GOLD and STAR severity classes within the cohort of study participants, noting that 53.2% were shown to be in coinciding categories. The evaluation implemented the Bangdiwala B value, calculated at 0.775 with linear weights. Over the course of the up to 95-month monitoring period, the median period duration being 54 months, death was reported among 20.5% of the subjects.

The research team’s Univariate Cox proportional hazards analyses indicated there had been a significant discrepancy in mortality rates between the GOLD 1 and GOLD 3 and 4 groups, with the GOLD 1 group being the team’s reference [hazard ratio 4.222 (95% CI 1.298–13.733), P = .017]. The team did not, however, identify a statistically significant predictive correlation between STAR 1 and STAR 2, or between STAR 1 and STAR 3 and 4.

As far as subjects’ health-related quality of life, the investigators reported major differences in scores on the St. George’s Respiratory Questionnaire (SGRQ) Total and in the COPD Assessment Test (CAT) among the various GOLD arms of the study, with the exception being in the CAT score comparison between GOLD 1 and 2.

Another note made by the team was that there had been distinctions in SGRQ Total and CAT scores between the STAR 1 and STAR 3 and 4 arms, but there were not any substantial distinctions found between STAR 1 and 2 for such metrics.

Therefore, the investigators would conclude that the GOLD classification performed better than the STAR classification as far as evaluations of COPD-specific health status measurements, including the SGRQ Total and the CAT score.

“Despite the different analyses, many studies have shown that the SGRQ and CAT scores are significant mortality predictors,” they wrote. “Therefore, as determinants of COPD severity, mortality prediction and health status may have some similarities in terms of patient categorization although they are assessed in different ways.”

References

1. ^{Nishimura K, Kusunose M, Shibayama A, Nakayasu K. Comparison of Disease Severity Classifications of Chronic Obstructive Pulmonary Disease: GOLD vs. STAR in Clinical Practice. Diagnostics. 2024; 14(6):646. https://doi.org/10.3390/diagnostics14060646.}
2. ^{Nishimura, K.; Kusunose, M.; Sanda, R.; Mori, M.; Shibayama, A.; Nakayasu, K. Comparison of Predictive Properties between Tools of Patient-Reported Outcomes: Risk Prediction for Three Future Events in Subjects with COPD. Diagnostics 2023, 13, 2269.}
3. ^{Nishimura, K.; Kusunose, M.; Shibayama, A.; Nakayasu, K. Is Frailty a Mortality Predictor in Subjects with Chronic Obstructive Pulmonary Disease? Int. J. Chronic Obstr. Pulm. Dis. 2023, 18, 2955–2960.}