Compute the GOLD 2026 spirometric airflow-limitation grade (GOLD 1-4) from post-bronchodilator FEV1 percent predicted. This helper implements the spirometric grading component of the GOLD COPD framework; it does not diagnose COPD.
Arguments
- fev1_pctpred
Numeric vector of post-bronchodilator FEV1 percent-predicted values (e.g. the
fev1_pctpred_2022column frompft_spirometry()computed from post-bronchodilator measured FEV1).- fev1fvc
Optional numeric vector of post-bronchodilator FEV1/FVC ratios, used to enforce the GOLD 2026 fixed-ratio prerequisite. When supplied, rows with
fev1fvc >= 0.70are returned asNA_character_, because GOLD 2026 Figure 2.10 applies the grades only when post-bronchodilator FEV1/FVC < 0.70. When omitted (the defaultNA_real_) or all-NA, no prerequisite check is performed and a grade is returned for every non-NAfev1_pctpred; this preserves backward-compatible behaviour, and the caller is then responsible for restricting use to tests that meet the prerequisite.
Value
Character vector with values "GOLD 1", "GOLD 2",
"GOLD 3", "GOLD 4", or NA. NA is returned for rows with
missing fev1_pctpred OR (when fev1fvc is supplied) rows that
do not meet the fixed-ratio spirometric prerequisite.
Details
A GOLD grade is not, by itself, a diagnosis of COPD. Per the GOLD
2026 report, a clinical diagnosis of COPD requires clinical context
(symptoms and/or exposure to risk factors) beyond spirometry, and
that clinical assessment is outside the scope of pft. pft_gold()
implements only the spirometric grade defined in Figure 2.10 of the
GOLD 2026 report; it does not implement the GOLD symptom/exacerbation
assessment or any treatment recommendation.
GOLD 2026 grades of airflow limitation, based on post-bronchodilator FEV1 (Figure 2.10 of the GOLD 2026 report, content page 38; labels as given by GOLD):
| Grade | GOLD label | Post-BD FEV1 % predicted |
| GOLD 1 | Mild | >= 80 |
| GOLD 2 | Moderate | >= 50 and < 80 |
| GOLD 3 | Severe | >= 30 and < 50 |
| GOLD 4 | Very severe | < 30 |
GOLD 2026 states the prerequisite "In patients with COPD (FEV1/FVC <
0.7)" explicitly above Figure 2.10's grade table, and the surrounding
text (content p. 37) repeats that a post-bronchodilator FEV1/FVC <
0.7 is required. Supplying fev1fvc enforces this fixed-ratio
spirometric prerequisite only; it does not establish a clinical
diagnosis. Callers wanting an LLN-based airflow-obstruction
criterion instead should use pft_classify() to identify tests
showing airflow obstruction and mask pft_gold() output by hand.
The grade boundaries are those of the GOLD 2026 report. They are not
updated automatically; any change to a future GOLD report would be
introduced in a versioned pft release.
Test phase (post-bronchodilator values)
GOLD 2026 defines both the grade and its fixed-ratio prerequisite on
post-bronchodilator spirometry: the grade uses post-bronchodilator
FEV1 percent predicted, and the prerequisite is post-bronchodilator
FEV1/FVC < 0.70. pft_gold() does not infer whether a supplied value
is pre- or post-bronchodilator; the caller is responsible for
supplying post-bronchodilator values for both arguments.
References
Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global Strategy for the Diagnosis, Management and Prevention of Chronic Obstructive Pulmonary Disease, 2026 Report. Figure 2.10. https://goldcopd.org.
See also
pft_classify() for LLN-based airflow obstruction
identification (Stanojevic 2022); pft_severity() for the
z-score-based severity scheme (which differs from GOLD's
percent-predicted scheme).
Examples
# Post-bronchodilator FEV1 % predicted for four tests.
post_fev1_pctpred <- c(85, 65, 40, 25)
# Without the prerequisite check (backward-compatible): one grade per
# non-NA input.
pft_gold(post_fev1_pctpred)
#> [1] "GOLD 1" "GOLD 2" "GOLD 3" "GOLD 4"
# -> "GOLD 1" "GOLD 2" "GOLD 3" "GOLD 4"
# With the fixed-ratio prerequisite: the third test has a
# post-bronchodilator FEV1/FVC of 0.75 (prerequisite not met) and is
# returned NA.
post_fev1fvc <- c(0.65, 0.60, 0.75, 0.55)
pft_gold(post_fev1_pctpred, fev1fvc = post_fev1fvc)
#> [1] "GOLD 1" "GOLD 2" NA "GOLD 4"
# -> "GOLD 1" "GOLD 2" NA "GOLD 4"