B-lines: to count or not to count?

We read with a great interest the paper by Miglioranza et al. (1), which sought to define the performance of lung ultrasound (LUS) compared with a clinical congestion score, natriuretic peptides, and echocardiography, to evaluate decompensation in patients with systolic heart failure (HF) in an outpatient clinic. This paper is a valuable effort to bridge the gap between echocardiography and thoracic ultrasound, and their separate skills and applicationda topic that is still quite controversial (2). Nonetheless, we remain skeptical about the value of this test. Four methodological observations seem relevant. First, the specificity of LUS B-lines is suboptimal: in addition to pulmonary congestion, these are visible in chronic obstructive pulmonary disease (3), pulmonary fibrosis (4), and lymphangitis (2,4). Second, the evaluation process is at best semiquantitative, because the method is more of a subjective overview than an actual “measurement.” Third, most reference studies have used linear or convex probes rather than phased array transducers; the use of phased-array transducers provides a greater risk of artifacts, depending on machine settings and particularly at lower frequencies. Finally, the actual interobserver and intraobserver measurement range is not reported (1). There are also some practical issues that warrant further attention. First, although the authors state that “this technique is faster to perform, is less expensive, and has lower technical requirements compared with a full echocardiography examination,” such a comparison of cost and return needs formal study. Second, the statement “LUS could be used as an extension of the physical examination and to differentiate hemodynamic from pulmonary congestion” warrants examination in a mixed patient group with pulmonary disease, to truly evaluate the ability to perform this differentiation. Third, in our opinion, the implication of the article that pharmacological therapy could be tailored as soon as the patient, although asymptomatic, shows a significant increase in the number of B-lines is speculative and not yet supported by solid evidence. In conclusion, we think that a critical reappraisal of this and other similar papers published on B-lines is mandatory. The evaluation of these artifacts using subjective scores is contrary to efforts to improve the reliability and objectivity of imaging (3–5).