Presentation in a prehospital setting means that imaging studies are not available. However, the authors assume that there is access to a portable ultrasound machine for evaluating the lungs.
Parameters:
(1) ultrasound examination of the lung
(2) serum N-terminal pro-brain natriuretic peptide (pro-NT-BNP, using the Cardiac Reader device from Roche Diagnostics)
(3) modified Boston criteria without imaging studies (see Modified Boston Criteria)
Ultrasonography was performed with examination of 8 lung zones, 4 on the left side and 4 on the right side (after Volpicelli et al and Liteplo et al). The endpoint was identification of B-lines ("comet sign" = hyperechoic reverberatio artifiacts at the pleural line which extend vertically on the screen):
(1) left anterior upper lung zone
(2) left anterior lower lung zone
(3) left lateral upper lung zone
(4) left lateral lower lung zone
(5) right anterior upper lung zone
(6) right anterior lower lung zone
(7) right lateral upper lung zone
(8) right lateral lower lung zone
Criteria for a positive ultrasound study:
(1) 3 or more B-lines ("comet tail sign") in a zone
(2) 2 or more positive zones on the left side and 2 or more zones on the right side (bilateral)
|
Parameter
|
Finding
|
Points
|
|
ultrasound study
|
negative
|
0
|
|
|
positive
|
1
|
|
serum pro-NT-BNP
|
<= 1,000 pg/mL
|
0
|
|
|
> 1,000 per pg/mL
|
1
|
|
modified Boston criteria
|
< 8
|
0
|
|
|
>= 8
|
1
|
number of parameters for heart failure present =
= SUM(points for all 3 parameters)
Interpretation:
• A patient with true heart failure should have all 3 parameters present.
• The odds ratio for a positive ultrasound study was 54 vs 14 for pro-NT-BNP.
• Ultrasound was used to decide if the patient had heart failure when the other measures were discrepant. This would work when the pro-NT-BNP was <= 1,000. The specificity of ultrasound was not 100%.
Performance:
• The authors claimed 100% sensitivity and 95% specificity for a positive ultrasound study.
• The sensitivity of the pro-NT-BNP was 92% and specificity 89%.
• The sensitivity of the modified Boston criteria was 85% and specificity 86%.
• The age of the patients with heart failure was different from the age of the patients with pulmonary disease, indicating different prevalences at different ages.
