Grade COPD severity by GOLD criteria

Returns the GOLD spirometric severity grade (1-4) for one or more patients given their FEV1 expressed as a percent of predicted, optionally enforcing the GOLD-mandated prerequisite of confirmed airflow obstruction (FEV1/FVC < 0.7).

Usage

pft_gold(fev1_pctpred, fev1fvc = NA_real_)

Arguments

fev1_pctpred

Numeric vector of FEV1 % predicted values (e.g. the fev1_pctpred column from pft_spirometry() when measured values are supplied).

fev1fvc

Optional numeric vector of post-bronchodilator FEV1/FVC ratios (e.g. the fev1fvc_measured column). When supplied, rows with fev1fvc >= 0.7 are returned as NA_character_ – per GOLD 2026 Figure 2.10, the grading applies only "In patients with COPD (FEV1/FVC < 0.7)". When omitted (the default NA_real_) or all-NA, no prerequisite check is performed and a grade is returned for every non-NA fev1_pctpred.

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 fail the airflow-obstruction prerequisite.

Details

GOLD severity grades for airflow obstruction (Figure 2.10 of the GOLD 2026 report, content page 38):

Grade	Severity	FEV1 % predicted
GOLD 1	Mild	>= 80
GOLD 2	Moderate	>= 50 and < 80
GOLD 3	Severe	>= 30 and < 50
GOLD 4	Very severe	< 30

GOLD specifies the prerequisite "In patients with COPD (FEV1/FVC < 0.7)" explicitly above Figure 2.10's grade table; the surrounding text (content p. 37) repeats this requirement. Supplying fev1fvc enforces the GOLD fixed-cutoff prerequisite. Callers wanting an LLN-based prerequisite instead should use pft_classify() to identify obstructed patients and mask pft_gold() output by hand.

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

# Without prerequisite check (backward-compatible): one grade per
# non-NA input.
pft_gold(c(85, 65, 40, 25))
#> [1] "GOLD 1" "GOLD 2" "GOLD 3" "GOLD 4"
# -> "GOLD 1" "GOLD 2" "GOLD 3" "GOLD 4"

# With prerequisite check: the third patient has FEV1/FVC = 0.75
# (no airflow obstruction) and is returned NA.
pft_gold(c(85, 65, 40, 25), fev1fvc = c(0.65, 0.60, 0.75, 0.55))
#> [1] "GOLD 1" "GOLD 2" NA       "GOLD 4"
# -> "GOLD 1" "GOLD 2" NA "GOLD 4"