CAN THE ASSESSMENT OF ULTRASOUND LUNG WATER IN HEMODIALYSIS PATIENTS BE SIMPLIFIED?

Background and Aims: Lung Ultrasound (US) reliably estimates lung water and it is increasingly applied in clinical practice in dialysis patients. Lung water is currently measured by applying a semi-quantitative US score summing up the US-B lines (an equivalent of B lines in standard X-rays of the thorax) detected in 28 lung intercostal spaces (LIS) (Jambrik Z et al., Am J Cardiol 2004; 93:1265-70). A simplified assessment restricted to 8 LIS only (Gutierrez M et al., Arthritis Research & Therapy, 2011;13:R134) has been proposed. However, the agreement among this simplified score and the reference score has not been studied and the prognostic value of the simplified score (8-LIS) has not been face to face compared with the 28-LIS score. Method: We included in the analysis in a cohort of 303 hemodialysis (HD) patients in which the pre-dialysis US-BL score was measured at baseline with both the semi-quantitative by Jambrik and the simplified Gutierrez method. The time needed for performing the 28-LIS and the 8-LIS score by six independent assessors with various experience -from low to high- on lung US assessment was accurately measured and recorded. Patients were divided into 4 categories, according to pre-established cut-offs specific for the two methods (28-LIS score: <5; 6-15; 16-30; >30 US-BL; 8-LIS score: <10; 11- 20; 21-50; >50 US-BL) The prediction power of these scores for death and fatal and non-fatal cardiovascular events was assessed by the explained variance (R2). Results: The 28-LIS score and the 8-LIS score were highly inter-related (Spearman’s q=0.93, P<0.001). During a mean follow-up of 3 years, 112 patients died and 129 experienced a CV event. At univariate and multivariate analysis, both scores were associated to the study outcomes (Tab.1). The explained variance (R2) of the 28-LIS score for death was 4.1% and that for CV events 4.6%. The corresponding R2 of the 8-LIS score were 5.4% (death) and 4.7%, (CV events), to values close to those of the 28-LIS score. Accordingly, when the two scores were separately added to a clinical model including easily available clinical variables (age, gender, smoking, diabetes, cardiovascular comorbidities, cholesterol, arterial pressure, BMI, anti-hypertensive treatment, NYHA class as well as dialysis vintage, hemoglobin, albumin, phosphate and CRP) the R2 of the model including the 28-LIS score (death: 31.1%; CV events: 23.9%) were again very similar to those of the 8-LIS score (30.7% and 23.1%, respectively). The median time needed to perform the examination was 3:05 min (IQR 2:22 – 5:00 min) for the 28 LIS score and 1:35 min (IQR 1:16 – 2:00 min) for the 8 LIS score. Conclusion: The simplified Gutierrez 8-LIS score is tightly related to the classical Jambrik 28 LIS score and the two scores hold an almost identical predictive power. Even though the 28-LIS score demands less than 5 minutes, the 8-LIS score can be done in only about 90 sec. and it is therefore better suited for application in everyday clinical practice in hemodialysis units.