Combination of lung ultrasound (a comet-tail sign) and N-terminal pro-brain natriuretic peptide in differentiating acute heart failure from chronic obstructive pulmonary disease and asthma as cause of acute dyspnea in prehospital emergency setting

Table 4 Test characteristics of ultrasound examination, modified Boston examination, NT-proBNP and combination of ultrasound examination and NT-proBNP^a

Characteristic	Ultrasound examination^b	Modified Boston criteria scoring	NT-proBNP	Ultrasound examination + NT-proBNP^c	P value^d
Sensitivity	100% (95% CI 98 to 100)	85% (95% CI 79 to 89)	92% (95% CI 88 to 95)	100% (95% CI 98 to 100)	< 0.01
Specificity	95% (95% CI 91 to 100)	86% (95% CI 82 to 90)	89% (95% CI 84 to 92)	100% (95% CI 97 to 100)	< 0.01
NPV	100% (95% CI 98 to 100)	80% (95% CI 77 to 85)	86% (95% CI 82 to 90)	100% (95% CI 98 to 100)	< 0.01
PPV	96% (95% CI 93 to 100)	90% (95% CI 86 to 93)	90% (95% CI 85 to 94)	100% (95% CI 96 to 100)	< 0.01
LR⁺	20 (95% CI 1.98 to 89.94)	6.1 (95% CI 1.65 to 18.48)	8.36 (95% CI 1.72 to 33.86)	Infinite	< 0.01
LR^-	0	0.18 (95% CI 0.07 to 0.52)	0.09 (95% CI 0.02 to 0.23)	0	< 0.01
AUROC	0.94 (95% CI: 0.90 to 0.97)	0.86 (95% CI 0.80 to 0.91)	0.90 (95% CI 0.84 to 0.94)	0.99 (95% CI 0.98 to 1.00)	< 0.01

^aNPV, negative predictive value; PPV, positive predictive value; LR⁺, positive likelihood ratio; LR^-, negative likelihood ratio; AUROC, area under receiver-operating curve; NT-proBNP, amino terminal pro-brain natriuretic peptide; UE, ultrasound examination. ^bUE alone was statistically significantly more accurate in diagnosing HF than the modified Boston criteria and NT-proBNP (better sensitivity, specificity, NPV, PPV, LR⁺, LR^- and AUROC; P < 0.01). ^cThe combination of UE and NT-proBNP was the supreme method in diagnosing HF in a prehospital setting; when compared with UE alone, it had equal results in sensitivity, NPV and LR^- (P = 0.99) and significantly better results in specificity, PPV and AUROC (P < 0.01). Compared with Boston modified criteria or NT-proBNP alone, UE + NT-proBNP was significantly better with regard to all characteristics (sensitivity, specificity, NPV, PPV, LR⁺, LR^- and AUROC; P < 0.01). ^dThe comparison of the four methods was done using the χ² test with the Bonferroni correction for multiple comparisons. The AUROC accuracy of UE (lung comet-tail sign); NT-proBNP; Boston criteria for diagnosing HF (clinical assessment); and the combination of ultrasound, NT-proBNP and Boston criteria were calculated and compared with univariate Z-score testing. AUROC was compared using the technique proposed by Hanley and Mc Neil [20] and Jannuzzi et al. [21].

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