Urea reduction ratio considering urea rebound

An American National Study shows that survival benefits from higher dialysis doses appear to be present up to a Kt/V level of 1.3 or a urea reduction ratio (URR) of 70%. The effect of increasing dialysis efficiency magnified urea rebound and the error in URR determinations. Several formulas have been developed to calculate URR considering the urea rebound (URRr). Smye and coworkers have proposed a method whereby the equilibrated blood urea nitrogen is predicted by additional intradialytic urea sample. Maduell and colleagues, based on analysis of postdialysis urea rebound, have proposed a method whereby the urea rebound is predicted. To compare measured URRr to estimated by Smye and Maduell formulas, 384 patients were studied, 211 males and 173 females, who received a dialysis session with their habitual parameters. Measurements of plasma urea concentration were obtained at the beginning, 90-100 min following the start of dialysis, at the end, and 45 min after dialysis. The postdialysis urea rebound was 22.4+/-9.7%. The urea kinetic model Kt/V was 1.365+/-0.26, and Kt/Vr was 1.14+/-0.23. URR was 68.7+/-6.6%, and when it was calculated with urea rebound, it decreased to 61.9+/-7.4%. The URRr correlated with calculations by Smye and Maduell formulas: 60.7+/-8.4 (r = 0.722, p < 0.001) and 61.8+/-6.6 (r = 0.933, p < 0.001), respectively. The precision of estimated limits of agreement and percentage of error by Bland and Altman analysis show that URRr estimated Maduell formula could be used in place of the URRr. Otherwise, the degree of agreement of the Smye method was not clinically acceptable. In conclusion, our results led us to suggest that in actual dialysis, the use of URR is not adequate for delivered hemodialysis dose, and URRr should be used. URRr estimated by Maduell formula could be a simple and accurate method for use in clinical practice. The recommended dialysis dose by the American National Study of URR of 70% could correspond, considering urea rebound, to Kt/Vr 1.18 or URRr of 64%.

Validation of different methods to calculate Kt/V considering postdialysis rebound

BACKGROUND

The effect of increasing dialysis efficiency magnifies rebound urea and the error in Kt/V determinations from single pool urea kinetics. Several formulae have been developed to calculate Kt/V taking into account the rebound urea (Kt/Vr). Smye et al. proposed a method whereby the equilibrated BUN is predicted by an additional intradialytic urea sample (Kt/VrSmye). Daugirdas et al. proposed a method where a single pool Kt/V is modified according to the speed of dialysis to obtain a double pool Kt/V (Kt/VrDaug). Maduell et al. developed a method based on analysis of post-dialysis urea rebound whereby the Kt/Vr is predicted according to the single pool Kt/V and K/V (Kt/VrMad).

DESIGN OF THE STUDY

We compared Kt/Vr estimated by these three formulae (Smye, Daugirdas, and Maduell) in 384 patients consisting of 211 males and 173 females, who received dialysis according to their regular protocols. Plasma urea was measured at the beginning, 90-100 min following the start of dialysis, the end, and 45 min post-dialysis.

RESULTS

Post-dialysis rebound urea was 22.4 +/- 9.7%. Kt/V and Kt/Vr obtained with rea kinetic model Kt/V 1.184 +/- 0.22 and 0.984 +/- 0.20, respectively. These was a good correlation between Kt/Vr and the Smye formula (Kt/VrSmye = 0.956 +/- 0.21, r = 0.729, P < 0.001), and a better one for Daugirdas (Kt/VrDaug = 0.984 +/- 0.18, r = 0.931, P < 0.001), and Maduell formulae (Kt/VrMad = 0.980 +/- 0.18, r = 0.946, P < 0.001). Limits of agreement and percentage of error estimated according to Bland and Altman show that Kt/Vr estimated by Daugirdas and Maduell formulae could be used in place of the Kt/Vr. The degree of agreement with the Smye method is not clinically acceptable.

CONCLUSION

Our results suggest that the use of a single pool Kt/V is not adequate to estimate the haemodialysis dose delivered and Kt/V taking rebound urea in consideration. Kt/Vr estimated by Daugirdas or Maduell formulae are a simple and accurate method for use in clinical practice.

Epidemiology of hepatitis C virus infection in patients with renal disease

This study was carried out to determine the prevalence of hepatitis C virus (HCV) antibodies and the epidemiologic factors associated with HCV infection in patients with chronic renal failure before the onset of ESRD. Sex, age, type of renal disease, level of renal function, and history of blood transfusions and invasive procedures were analyzed in 226 patients with renal disease, compared with a population of 1,244 normal subjects and 124 patients with impaired immunity (patients having autoimmune diseases and receiving chemotherapy treatment). Eighteen seropositive patients with renal disease (prevalence, 7.9%) were found, which was significantly higher than the prevalence in the normal population (1.03% in blood donors, 0.98% in pregnant women; P < 0.001, chi 2). There was no significant association of sex, number of blood transfusions, or history of invasive procedures with the presence of HCV antibodies. The prevalence of HCV antibodies was higher (16.6%) in patients with glomerulonephritis compared with patients diagnosed with interstitial nephritis, pyelonephritis, nephrosclerosis, diabetes mellitus, polycystic kidney, and miscellaneous renal diseases (P < 0.01, chi 2). There was a higher prevalence of HCV antibodies in patients with creatinine clearance lower than 30 mL/min (13%) compared with patients with creatinine clearance higher than 30 mL/min (2.7%) (P < 0.01, chi 2). These data suggest that HCV infection may be associated with the pathogenesis of glomerulonephritis. Alternatively, glomerulonephritis or severe renal insufficiency may increase the likelihood of HCV infection.

Epidemiology of hepatitis C virus infection in patients with renal disease

This study was carried out to determine the prevalence of hepatitis C virus (HCV) antibodies and the epidemiologic factors associated with HCV infection in patients with chronic renal failure before the onset of ESRD. Sex, age, type of renal disease, level of renal function, and history of blood transfusions and invasive procedures were analyzed in 226 patients with renal disease, compared with a population of 1,244 normal subjects and 124 patients with impaired immunity (patients having autoimmune diseases and receiving chemotherapy treatment). Eighteen seropositive patients with renal disease (prevalence, 7.9%) were found, which was significantly higher than the prevalence in the normal population (1.03% in blood donors, 0.98% in pregnant women; P < 0.001, chi 2). There was no significant association of sex, number of blood transfusions, or history of invasive procedures with the presence of HCV antibodies. The prevalence of HCV antibodies was higher (16.6%) in patients with glomerulonephritis compared with patients diagnosed with interstitial nephritis, pyelonephritis, nephrosclerosis, diabetes mellitus, polycystic kidney, and miscellaneous renal diseases (P < 0.01, chi 2). There was a higher prevalence of HCV antibodies in patients with creatinine clearance lower than 30 mL/min (13%) compared with patients with creatinine clearance higher than 30 mL/min (2.7%) (P < 0.01, chi 2). These data suggest that HCV infection may be associated with the pathogenesis of glomerulonephritis. Alternatively, glomerulonephritis or severe renal insufficiency may increase the likelihood of HCV infection.

Hepatitis C virus RNA in patients with anti-HCV on hemodialysis. Relationship to transaminase levels

This study was performed in patients with hepatitis C virus (HCV) who were treated with hemodialysis to determine the relationships among alanine amino-transferase (ALT) levels, immunoglobulin (Ig) G anti-HCV, IgM anti-HCV core, and HCV RNA. Of 107 patients on hemodialysis, 27 had positive IgG anti-HCV. Eight of the patients who had HCV were evaluated every 8 months during a period of 2 years, using the following selection criteria: positive IgG against c-22, c33-c, 5-1-1, and c100-3 viral peptides; absence of infection by hepatitis A virus, hepatitis B virus, cytomegalo-virus, Epstein-Barr virus, herpes simplex virus, and human immunodeficiency virus, as well as absence of hepatotoxic drugs or cholelithiasis. We considered elevated ALT values as those more than 150% of the upper limit of normal. Three of the patients had persistent elevation of ALT levels, two had alternating elevation of ALT levels, and three had normal ALT levels in all blood samples. Of the 24 blood samples, 11 had elevation of ALT (45.8%) levels that showed positive IgM anti-HCV, but only 7 of these 11 had positive HCV RNA (63.6%). None of the 13 blood samples without elevation of ALT had positive IgM anti-HCV, but 5 had positive HCV RNA (38.5%). We found an excellent correlation between IgM anti-HCV and ALT levels (r = 0.81). There was no statistically significant difference between the mean ALT values on the 12 blood samples that had positive HCV RNA and the mean ALT values of the negative HCV RNA samples (53.5 +/- 28.0 IU/l vs. 37.4 +/- 17.5 IU/l, respectively). IgM anti-HCV is related to the elevation of ALT levels and can be used as a serologic marker to indicate the presence of active HCV induced liver damage. Serum ALT levels do not correlate with the detection of viral genome in sera. IgG anti-HCV is not necessarily associated with HCV RNA or IgM anti-HCV. The absence of IgM and HCV RNA in patients with IgG anti-HCV and normal ALT levels does not necessarily suggest the absence of active HCV infection.