Table 2.

Studies comparing index test to a microbiological reference standard

References	Study population				Index test	Reference test	Results (95% confidence interval where available)
	Country	n =	Mean age	M:F ratio
Albert et al. [57]	Canada	705	58.9	2.9	Gram stain of either ETA or BAL	same sample (ETA or BAL) positive culture result for pathogenic bacteria any quantity	Sens = 74% Spec = 72% κ = 0.36 (0.31–0.40)
Anand et al. [56]	USA	105	51.5	1.4	sTREM-1 ELISA in BAL	BAL culture > 103 CFU/mL	Sens = 42.1% Spec = 75.6%
Baldesi et al. [55]	France	127	62.5	2.3	BAL culture > 104 CFU/mL (uncorrected for dilution factor)	BAL culture > 104 CFU/mL (corrected for dilution factor using plasma/BAL urea)	Sens = 97.7% Spec = 98%
Carvalho et al. [54]	Brazil	22	59.41		comparison of three sampling techniques (ETA, miniBAL, and BAL)	No mention which is considered index test or reference standard	Sens = NR Spec = NR
Clavel et al. [51]	France	120	65	3.1	qPCR from BAL equivalent to > 104 CFU/mL and qPCR from ETA equivalent to > 106 CFU/mL	BAL culture > 104 CFU/mL or ETA culture > 106 CFU/mL	qPCR from BAL Sens = 89.2% Spec = 97.1% qPCR from ETA Sens = 71.8% Spec = 96.6%
Conway Morris et al. [74]	UK	72	57	1.5	BAL IL-1β and IL-8	BAL culture > 104 CFU/mL	Sens = 94% Spec = 64%
Douglas et al. [50]	USA	33	55	N/R	Mini BAL automated microscopy	Mini BAL culture > 104 CFU/mL	Sens = 100% Spec = 97%
Elmahalawy et al. [49]	Egypt	40	45.4	3.0	Pentraxin 3 ELISA in BAL	BAL culture > 104 CFU/mL	Sens = 96.7% Spec = 100% AUROCC = 0.966 (0.985 to 1)
Fujitani et al. [47]	USA	256	57.5	2.1	ETA culture	Mini BAL culture > 104 CFU/mL	Sens = 65.4% Spec = 56.1% κ = 0.22 (0.17–0.27)
Gedik et al. [46]	Turkey	31	56	1.4	ETA culture > 105 CFU/mL	Mini BAL culture > 104 CFU/mL	κ = 0.804, p = 0.005
Goldberg et al. [45]	USA	229	49	2.0	Gram stain of BAL	BAL culture > 105 CFU/mL	Sens = 90% Spec = 67%
Guler et al. [43]	Turkey	50	52	2.1	Modified CPIS	BAL culture > 104 CFU/mL	CPIS > 7 Sens = 80% Spec = 17% CPIS > 6 Sens = 76% Spec = 15% CPIS ≥ 6 Sens = 80.7% Spec = 16.6% CPIS ≥ 5 Sens = 80% Spec = 10%
Hashimoto et al. [42]	Japan	51	41	1.4	Semi-quantitative Gram stain or culture of ETA or BAL (not otherwise specified)	ETA culture > 106 CFU/mL	Gram stain Sens = 95% Spec = 61% κ = 0.59 (0.45–0.72) Culture Sens = 96% Spec = 40% κ = 0.4 (0.25–0.54)
Hellyer et al. [41]	UK	150	56.3	2.9	BAL IL-1β and IL-8	BAL culture > 104 CFU/mL	Sens = 100% Spec = 44.3%
Jackson et al. [40]	USA	73	52	3.5	BAL—unilateral	BAL—bilateral	Sens = 73% Spec = 82%
Jiao et al. [65]	China	92	48	1.0	Serum PCT Serum IL-6 Serum CRP	BAL culture > 104 CFU/mL	PCT Sens = 91% Spec = 71% IL-6 Sens = 58% Spec = 64% CRP Sens = 52% Spec = 74%
Jung et al. [63]	France	57	61	2.2	BAL Procalcitonin	BAL culture > 104 CFU/mL	Sens = 94% Spec = 75%
Kneidinger et al. [60]	Austria	132	62	2.1	BAL culture > 104 CFU/mL after 24 h storage at 4 °C and after storage at − 80 °C	BAL culture > 104 CFU/mL after immediate culture	Immediate culture vs delayed culture (4 °C) Sens = 96.5% Spec = 100% Immediate culture vs delayed culture (− 80 °C) Sens = 50.4% Spec = 100%
Kwon et al. [59]	Korea	64	65	2.6	qPCR of BAL fluid or bronchial washings	BAL culture > 104 CFU/mL or bronchial washing > 105 CFU/mL	Sens = 88.9% Spec = 88.9%
Leo et al. [58]	Mexico	21	42	2.0	mini BAL (using cut NG tube) > 104 CFU/mL	BAL culture > 104 CFU/mL	Sens = 92.8% Spec = 85%
Linssen et al. [67]	USA	117	N/R	N/R	BAL PCT and CRP	BAL culture > 104 CFU/mL or > 2% cells with intracellular organisms	PCT AUCROCC = 0.448 CRP AUCROCC = 0.477
Linssen et al. [75]	USA	282	60.3	2.1	Various BAL cytological parameters including total cell count, alveolar macrophages, lymphocytes, neutrophils, eosinophils, mast cells, infected cells; in isolation or in combination	BAL culture > 104 CFU/mL	AUROCC for various cytological parameters Total cell count = 0.647 Alveolar macrophages = 0.313 Lymphocytes = 0.381 Neutrophils = 0.705 Eosinophils = 0.589 Mast cells = 0.557 Infected cells (%) = 0.904 AUROCC for combinations of cytological parameters Infected cells (%) + PMNs (%) = 0.892 Infected cells (%) + Total cell count = 0.890
Luna et al. [69]	Argentina	283	71.3	1.1	ETA culture > 103 CFU/mL	BAL culture > 104 CFU/mL	Sens = NR Spec = NR
Luyt et al. [70]	France	41	60	2.4	serum PCT 1st day of clinical suspicion of VAP	BAL culture > 104 CFU/mL	Sens = 72% Spec = 24%
Mongodi et al. [73]	France	99	66	3.7	Vplus-Eagram (ventilator-associated pneumonia lung ultrasound score and gram stain of ETA)	BAL culture > 104 CFU/mL	Sens = 81% Spec = 41%
Oudhuis et al. [66]	Netherlands	207	62	1.7	ETA culture > 105 CFU/mL	BAL culture > 104 CFU/mL or > 2% cells with intracellular organisms	Sens = 65% Spec = 48%
Refaat et al. [76]	Egypt	66	NR	NR	BAL composite biomarker (CRP, PCT, neutrophils, MIF, sTREM-1, suPAR)	BAL culture > 10 CFU/mL	Sens = 76% Spec = 62%
Schnabel et al. [48]	Netherlands	100	61.3	2.3	VOC in exhaled breath	BAL culture > 104 CFU/mL or > 2% cells with intracellular organisms	Sens = 75.8% Spec = 73.0%
Scholte et al. [77]	Netherlands	311	NR	NR	ETA Gram stain ETA Culture BALF Gram stain	BAL culture > 104 CFU/mL or > 2% cells with intracellular organisms	ETA Gram stain Sens = 65% Spec = 72% ETA Culture (any threshold) Sens = 82% Spec = 42% BALF Gram stain (> 0) Sens = 82% Spec = 66%
Vanspauwen et al. [79]	Netherlands	196	58.8	1.7	BAL Clara Cell protein 10 ELISA	BAL culture > 104 CFU/mL or > 2% cells with intracellular organisms	AUROCC of 0.586 (0.496–0.676)
Yagmurdur et al. [82]	Turkey	59	71	0.73	ETA culture > 104 CFU/mL	BAL culture > 104 CFU/mL	Sens = 60% Spec = 39%
Zagli et al. [83]	Italy	221	56	2.7	Chest Echography and Procalcitonin Pulmonary Infection Score > 5	ETA culture > 104 CFU/mL	Sens = 80.5% Spec = 85.2%