Table 2.

Summary of measurement properties of PROMs for cough assessment in IPF.

Measurement tool	References	Population	Psychometric properties	Results
Cough-specific instruments
LCQ	Key et al. (11)	19 participants with IPF	Construct validity	Spearman's correlation coefficients for objective cough frequency and LCQ total r −0.80 (p < 0.001) and LCQ physical r 0.76 (p < 0.001)*
		DLCO% 43.2 ± 16.06, FVC% 78.5 ± 24.4
	Morice et al. (77)	45 participants (29 with IPF) TLCO% 49 ± 16	Construct validity	Correlations between LCQ domains and measures of disease severity were weak and non-significant.
			Test-retest reliability	ICCs for total and domain scores ranging from 0.37 to 0.58
VAS	Key et al. (11)	19 participants with IPF DLCO% 43.2 ± 16.06, FVC% 78.5 ± 24.4	Construct validity	Spearman's correlation coefficients for objective cough frequency and VAS for cough severity*
				Day cough rate r = 0.8 (p < 0.001) and night cough rate r = 0.71 (p = 0.001).
CQLQ	Lechtzi et al. (78)	20 participants with IPF	Internal consistency	Cronbach's a >70 for total score and 4/6 subscales
		DLCO% 57.4 ± 14.4, FVC% 70.4 ± 13.7	Test-retest reliability	ICC for total score at baseline and week 15 0.88 (p < 0.01)
			MID	MID was 5.7 (95% CI, 4.9-6.4)
CASA-Q	Gries et al. (79)	18 participants with IPF DLCO% 48.7 ± 15.1, FVC% 87.2 ± 30.7	Content validity	†Intended meaning of each item clearly understood (89–100%).
				Items perceived to be highly relevant
				Recall period accurately used 89%.
Disease-specific instruments with cough domains or items relevant to cough
ATAQ-IPF	Horton et al. (80)	95 participants with IPF	Internal consistency	†Cronbach's a 0.92, Rasch model reliability 0.83
		DLCO% 39 ± 15, FVC% 65 ± 17,
ATAQ-IPF-cA	Birring et al. (81)	139 participants with IPF	Construct validity	Two items were removed due to floor effects
		DLCO% 42.2 ± 11.9 – 43.2 ± 16.5,
		FVC% 70.1 ± 17.7 – 80.7 ± 9.2‡	Internal consistency	†Internal consistency Cronbach's a 0.92
L-IPF	Swigris et al. (82)	125 participants with IPF DLCO% 50 ± 20, FVC% 71 ± 20	Construct validity	Correlation between L-IPF cough domain and SGRQ symptom domain 0.67. Correlations between L-IPF domain for cough and disease severity significant.
			Internal consistency	†Internal consistency ω coefficient > 0.93
			Test-retest reliability	†ICC 0.85
SGRQ-I	Prior et al. (83)	150 participants with IPF	Internal consistency	†Cronbach's a 0.77
		DLCO% 48.4 ± 14.1, FVC% 87.2 ± 23.1	Test-retest reliability	†ICC 0.78

ATAQ-IPF, A Tool to Assess QOL in IPF; ATAQ-IPF-cA, A Tool to Assess QOL in IPF Cross Atlantic; CASA-Q, Cough and Sputum Assessment Questionnaire; CQLQ, Cough Quality-of-Life Questionnaire; DLCO, diffusing capacity for carbon monoxide; FVC, forced vital capacity; ICC intraclass correlation coefficient; IPF, idiopathic pulmonary fibrosis; LCQ, Leicester Cough Questionnaire; L-IPF, Living with Pulmonary Fibrosis Questionnaire; MID, minimally important difference; SGRQ-I, IPF-specific version of the St George's Respiratory Questionnaire; TLCO, transfer factor for carbon monoxide; VAS, Visual Analog Scale; %, percentage predicted.

^*Evaluated in IPF.

^†Results for cough domains quoted.

^‡Results expressed as range of means for United Kingdom and United States of America populations.

Results expressed as mean ± standard deviation or mean ± standard error.