Inter-Vendor differences in speckle tracking strain - A ten year follow-up on the Strain Standardization Task Force Inter-Vendor Comparison Study

Abstract Background Global longitudinal strain (GLS) derived from two-dimensional speckle-tracking echocardiography is feasible and accurate. Nonetheless, in 2013, the Inter-Vendor Comparison Study showed significant differences of measurement results among vendors. In order to make tracking-based strain imaging a clinically accepted and useful parameter, it is of outmost importance to have interchangeable and accurate measurement results from all vendors. Purpose To investigate if the efforts of the EACVI/ASE/Industry Task Force to Standardize Deformation Imaging have led to a reduction of inter-vendor differences during the past ten years. Methods In an unique setting, in one single room, 372 echocardiographic examinations were performed in sixty-two subjects (50 male, age 56.1 ± 16.98) with a wide range of left ventricular (LV) function (ejection fraction from 30% to 64%) using ultrasound systems from six manufacturers. Each subject was scanned consecutively on all machines by the same assigned experienced sonographer. For each subject two image sets of LV apical views were acquired in order to assess reproducibility in a true test-retest setting. We assessed mean GLS (GLSAV) as average peak systolic global strain from the three apical views on five vendor-specific and five vendor-independent software solutions. We measured endocardial and mid-/full-wall GLS. Since there is no gold standard method to measure GLS, we compared GLSAV of each vendor to the average of the GLS values only from vendors that provide tracking software solutions (SWS) for clinical use. Results For both endocardial (Figure 1) and mid-/full-wall (Figure 2) GLS measurements from clinical SWS were comparable and within a very narrow range (mean GLS of vendors 17.25 ± 0.3% and 15.36 ± 0.3% respectively). The maximum absolute difference between all SWS was 4.1% and 4.9% strain units for endocardial and mid-/full-wall GLS respectively. GLSAV of each software versus the mean of clinical SWS showed significant correlation for most of the companies (r² >0.8, p<0.001). Test-retest variability of GLS measurements expressed as relative mean error was good and lower than for LV ejection fraction (6.3% on average for mean GLS and 7% for LV ejection fraction, p>0.05). Conclusions Our data show a substantial inter-vendor bias in GLS measurements. Nevertheless, in contrast to the situation ten years ago, companies that provide tracking software solutions for clinical use provide now very similar GLS values. In addition, most companies do now allow mid-/full-wall tracking. Our data indicate that the efforts of the strain standardization task force have been fruitful. A continuing effort is needed until all software providers adhere to the task force consensus recommendations.Figure 1Figure 2