Table 2.

Studies of Biomarkers for Frailty in Lung Disease

Systemic inflammation Frailty is generally associated with inflammatory biomarkers in lung disease
Patient Population	Finding
COPD	Frail patients had greater inflammation compared with those who were not (CRP 4.1±1.6 vs 3.2±2.8, p=0.021; Fibrinogen 3.6±1.3 vs 3.4±1.3, p=0.028)13
Lung transplant candidates	Frail patients had higher levels of IL-6 (SPPB, p = 0.10; FFP, p = 0.003) and tumor necrosis factor receptor 1 (SPPB, p = 0.001; FFP, p = 0.001) compared to those who were not11
Lung transplant candidates	No significant differences in analyzed cytokines (IL-10, IL-6, IL-2, IL-7, Il-12, IL-23, IL-18) among moderately frail compared to severely frail patients15
Hemoglobin Lower hemoglobin levels are associated with frailty in lung disease
ILD	Frail patients had a lower hemoglobin level (g/L) compared to those who were not(142±17 not-frail vs 137±19 frail, p <0.05)10
Lung transplant candidates	Frail subjects had a lower hemoglobin level (g/dl) compared to those who were not (SPPB: 12.0±1.9 frail vs 13.4±2.0 not frail, p= 0.004; FFP: 12.5±1.8 frail vs 13.2±2.0 not frail, p=0.001)11
Creatinine There is insufficient study of the relationship between frailty and creatinine levels in lung disease; inconsistent findings to date
ILD	Frail patients had a lower creatinine level (umol/L) compared to those who were not (70±18 frail vs 83±15 not frail, p<0.05)10
Lung transplant candidates	Differences in creatinine level were not significant among those who were frail compared to those who were not (SPPB: 0.9±0.5 frail vs 0.8±0.2 not frail, p=0.83; FFP: 0.8±0.3 frail vs 0.8±0.2 not frail, p=0.62)11
Albumin There is insufficient study of the relationship between frailty and albumin in lung disease, but findings to date support a relationship
ILD	Frail patients had lower albumin levels compared with those who were pre-frail or not frail (43±4 not frail, 44±4 pre-frail, 40±4 frail, p<0.05)10
Leptin There is insufficient study of the relationship between frailty and leptin in lung disease, but findings to date support a relationship
Lung transplant candidates	Frail patients tended to have lower leptin levels compared to those who were not (SPPB, p = 0.33; FFP, p = 0.08)11
Insulin-like growth factor 1 (IGF-1) There is insufficient study of the relationship between frailty and IGF-1 in lung disease, but findings to date support a relationship
Lung transplant candidates	Frail patients tended to have lower levels of IGF-1 compared to patients who were not (SPPB, p = 0.03; FFP, p = 0.16)11

^*COPD= chronic obstructive pulmonary disease; CRP= c-reactive protein; FFP= fried frailty phenotype; ILD= interstitial lung disease; IQR= interquartile range; SPPB= short physical performance battery