Probing the dry weight (DW) was largely dependent on clinical subjective estimates until recently. New bedside non-invasive tools have been developed with the aim of providing more objective information on volume status and guiding physicians in the quest for DW. Among them, bioimpedance (BIA) appears to be very promising.
Very recently, a BIA test aimed at assessing DW in hemodialysis (HD) patients has been developed, the “RE.sistance S.tabilization T.est” (REST) (Basile C et al, J Nephrol DOI 10.1007/s40620-014-0159-8, 2014). It is called BIA DW. Its rationale is based on the achievement of the flattening of the curve of the ratio R0/Rt (R0 is resistance at time 0 and Rt is resistance at a given time t during the HD session) of less than + 1% over 20 minutes in the presence of ongoing ultrafiltration.
Casistica e Metodi
A study group is being created (REST/Collaborative Study Initiative, ClinicalTrials.gov; study number NCT02446535).
Study protocol: the Clinical DW is the gold standard by definition. It is determined under strict clinical surveillance by the same attending physician. She/he will be helped by a clinical score of volume state about symptoms and signs of hypo- or hypervolemia, as described in Table 2 of the article by Kraemer M et al (Kidney Int 69: 1609 – 20, 2006). Then, this Clinical DW will be compared with BIA DW, as obtained after performing REST.
The preliminary analysis of the first 13 consecutive patients who finished the study is reported in Figure 1. A good agreement between Clinical and BIA DW is shown at the Bland-Altman plot, thus allowing a reciprocal validation of the two methods.
Clinical methods are fundamental in probing the DW. They must be supported by strict BIA protocols. REST appears to be a (the) brilliant solution in solving the old problem of DW in HD patients.