This study registered annually the number of seroconversions (SC) referred to the mean of center prevalence and the isolation measures use and risk factors. Finally the number of patients starting and ending dialysis was also studied.

Due to we find a sig. decrease of the prevalence during the years of study oh the prevalence and incidence global and more in HD and due to the high rate of population were included in center with isolation measures, we considered convenient to analize since 1993 the factors that influency in prevalence decrease, for this we choice the centers with equal isolation condition since 1993-1999, considering x prevalence of the centers (inicially and annually), seroconversions, time factor and isolation and change of it.

We used four quartils of prevalence in the first study and the patients were divided according the isolation and/or change of this in the years of study. (Statistical test Manova and Tuquey)

	1991	1992	1993	1994	1995	1996	1997	1998	1999
# patients	5218	5441	5644	6583	7135	7326	8489	9088	9507
Overall prevalence %	28,72	28,21	25,83	25,27	22,24	20,39	18,90	17,22	15,77
HD prevalence	36,07	33,37	28,03	27,04	24,15	21,89	20,24	18,03	16,27
CAPD prevalence	10,60	13,42	11,09	10,54	10,17	8,86	9,01	8,05	10,75
Home HD prevalence	38	17,60	17,07	16,60	32,35	25,71	22,95	32,55	25
Incidence %		3,2	1,6	1,9	0,67	0,8	0,47	0,41	0,26
# seroconversions		141	80	79	48	59	36	38	20
% centers Isolation meas.		29,8%	33,2%	50,1%	60,5%	67,3%	72,5%	77,9%	88,2%
SC/isolation /non-isolation		20/121	39/40	29/49	19/29	15/28	10/25	23/15	10/9
Mean prev. centers with SC		33,77	33,66	33,65	32,48	27,34	25,9	24,28	21,9
Mean prev c. without SC		26,74	24,17	22,9	20,58	18,59	18,3	16,75	16,14
Mean prev isolat/non is.	23,1/32,9	24,9/32,1	26,1/29,7	24/31,8	22,6/25,6	20,7/24	19,5/22,1	17,3/22,4	17/16,8

In the last years an % > 10% starting dialysis with Ac HCV+.

We find in Manova significant p 0,0001 between time and global prevalence and HD prevalence appearing interaction between time ans isolation p0,014.

Using Tuquey test we find decrease sig. in all years in the HD patients dialysed in center without isolation measures and starting isolation in 1994 p(<0,01).

Conclusions:

• 1) The HCV prevalence in Dialysis and more in HD is high, decreasing throughout the study.
• 2) Prevalence is higher in HD than CAPD patients.
• 3) HCV incidence decreases during the study.
• 4) The number of centers adopting isolation measures (principally in monitor) increased since 1991.
• 5) The mean prevalence in centers with seroconversions and in centers without isolation is higher than the centers with them.
• 6) The high prevalence is a risk factor for HCV seroconversion in each center. For this reason, universal precaution and isolation measures may be critical in these centers.
• 7) The factor Time appear with sig. Influence in prevalence decrease.
• 8) We found interaction between Time and Isolation factors.
• 9) The change the not isolation to isolation appear a sig. Influence in decrease HCV prevalence