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| Journal of Vascular Access 2002; 3: 158 - 163 |
| The role the type of vascular access plays in the transmission of hepatitis C virus in a high prevalence hemodialysis unit |
A.K. Saxena1, B. R. Panhotra2, D.S. Sundaram3
1Division of Nephrology, Department of Post-graduate Medicine, King Fahad Hospital and Tertiary Care Center, Hofuf - Saudi Arabia
2Department of Microbiology and Infection Control, King Fahad Hospital and Tertiary Care Center, Hofuf - Saudi Arabia
3Division of Nephrology, Post-graduate Department of Medicine
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ABSTRACT
Background: The necessity of having a vascular access site as well as extracorporeal blood circulation, may add to the risk for patients being dialyzed in units with high HCV prevalence of acquiring hepatitis C virus (HCV) infection. This study endeavors to determine the role the type of vascular access plays in the transmission of HCV infection in the hemodialysis (HD) unit of a Middle Eastern country.
Methods: The records of 198 patients with end-stage renal disease (ESRD) enrolled on maintenance HD from November 1995 to November 2000 at this tertiary care center, were retrospectively reviewed to match the HCV prevalence and seroconversion rates among patients groups being dialyzed through various types of vascular accesses. Factors such as, number of units of blood transfused and dialytic age (time-span since the initiation of the HD treatment), implicated in transmission of HCV infection in HD units, were also recorded, and compared among these cohorts.
Results: The overall, high HCV seroprevalence of 43.4% (86/198) and annual seroconversion rate of 8.6% per year were recorded. Patients with arteriovenous fistula (AVF) documented peak anti-HCV prevalence [61.7% (63/102)] and annual seroconversion rates (12.3%) as compared to lowest prevalence of 12.9% (4/34) and seroconversion rate of 2.5%, observed among patients with permanent Catheters (PC). Patients dialyzed through polytetrafluoroethylene (PTFE) grafts recorded the next highest HCV prevalence of 47.8% (11/23) with seroconversion rate of 9.5% but temporary catheter (TC) group had HCV prevalence of 19% (8/42) and seroconversion rate of 3.8% [Odd Ratio (OR)-1.58, 95% Confidence Interval (CI) (0.37-7.12), p-NS].
Conclusions: Considerably higher annual seroconversion rates in AVF [OR-10.90, 95% CI (3.2-40.0), p<0.0001] and PTFE [OR-5.71, 95% CI (1.31-26.79), p<0.016)] groups, appear to suggest that the patients being dialyzed through AVF and PTFE, carried significantly higher risk of acquisition of HCV infection compared to those dialyzed through TC and PC (reference group). This could possibly be attributed to likely accessibility of HCV to blood circulation due to possible breakdown of standard infection control precautions during repeated punctures and cannulations of AVF and PTFE to perform a HD, in a unit with high baseline HCV prevalence. (The Journal of Vascular Access 2002; 3: 158-63)
Key Words. HCV infection, Types of vascular access, Seroconversion, Prevalence, Hemodialysis
INTRODUCTION
Hepatitis C virus (HCV) infection has become a major cause of morbidity and mortality in patients on long-term hemodialysis (HD). There is a high incidence of it in the Middle and Far Eastern countries (1-3). The risk of HCV disease is rising for immunocompromized patients on long-term HD, in terms of development of chronic liver disease, cirrhosis and hepatocellular carcinoma. At the same time the cost of ESRD management has increased enormously (4).
A number of risk-factors have been recognized for HCV transmission among the patients on HD, including multiple blood transfusions, dialytic age (time-span from initiation of HD treatment), dialyzer reuse and hygiene in HD units; nosocomial transmission has been reported as the key mode of HCV infection in the modern hospital-based HD setup (5-10). HD creates a high-risk environment for the nosocomial transmission of HCV infection. Nevertheless, vascular access sites and extracorporeal blood circuit are indispensable and may conceivably add to the risk of acquiring HCV infection through nosocomial transmission while receiving treatment in a hospital-based HD unit, with high HCV prevalence.
The present study was designed to determine the role of vascular access in the transmission of HCV infection in high prevalence units. The HCV prevalence and seroconversion rates among ESRD patients being dialyzed with various types of vascular accesses was estimated.
Patients and Methods
This retrospective cohort study was carried out by reviewing the records of 198 ESRD patients of diverse etiologies enrolled for long-term HD from November 7, 1995 to November 6, 2000 at King Fahad Hospital and tertiary care center, Hofuf, Saudi Arabia. The mean age of the patients was 47.0 ± 17.5 years (range 15-84 years). There were 107 (54.0%) males and 91 (46.0%) females. All ESRD patients had been on HD for a mean dialytic age of 39.5 ± 7.25 months (range 4-102 months).
These ESRD patients were dialyzed two or three times per week using disposable single-use high-flux dialyzer membranes (polysulphone, Bellco, Mirandola, Italy; polyacrylonitrile, Filtrat 10 AN 69, Hospal, Meyzieu, France) and blood lines, in a common room without any partition between HCV positive and HCV negative patients. However, male and female patients were dialyzed in separate rooms and the patients with HBV infection were strictly isolated as per Centers for Disease Control (CDC) guidelines (11). HD staff nurses were not specifically assigned according to the serological status of patients during this period. The patient/ nursing staff ratio was 3:1 and the same staff nurse took care of HCV positive and HCV negative patients, adhering to the strict universal infection control precautions.
Types of vascular accesses used for HD
The break-down of the various types of vascular accesses used in the HD cohort, at this center, was as follows: a) 102 arteriovenous fistula (AVF); b) 23 polytetrafluoroethylene (PTFE) grafts; c) 42 permanent tunneled cuffed catheters (PC); d) 31 temporary Catheters (TC) i.e. Subclavian/Femoral/ Internal Jugular-dual lumen catheters. Thus the majority of the patients [51.5% (102/198)] were dialyzed through AVF, 11.6% (23/198) by means of PTFE grafts with 15.6% (31/198) via PC and the remaining 21.2% (42/198) using TC. Vascular catheters (TC and PC) were being used as an interim bridging solution to permit creation, maturation and revision of arteriovenous fistula (AVF) as well as a long-term solution in patients with exhausted vascular access sites or else intended for comfort in elderly ESRD patients having co-morbid conditions leading to limited life expectancy. Appropriate skin disinfection, stringent asepsis and the maximal antiseptic barriers were adopted at the time of vascular access placement and subsequent usage, especially during initiation and termination of HD. In addition, catheter hubs were also protected against environmental contamination through antiseptic gauze, at all times.
Infection control precautions
Strict adherence to universal precautions for infection control as recommended by Kellerman, and Alter CDC, Atlanta (12) were practiced routinely for all patients irrespective of their serological status for HCV or HBV, in our HD center.
Disinfection of hemodialysis machines
The HD machines used for HCV positive patients were used after chemical and hot water disinfection for the HCV negative patients. A strict protocol of careful chemical disinfections as per instructions of the manufacturers using Citrosteril, run at 85°C for 35 minutes after each dialysis session was adopted before using the machine for the next patient. Hot water, at 80-90°C, was run at high flow rate after full chemical disinfections for 60 minutes. This procedure was performed at the end of the day on every machine in preparation for the next day’s work while disinfection of dialysate circuit was performed with sodium hypochlorite after each individual session. External, disposable venous and arterial pressure transducer filters were also changed and discarded between each patient treatment after single use.
Blood samples were collected from all the HD patients and serum was stored at –20 °C till analyzed for anti HCV antibodies by second generation enzyme-linked immunosorbant assays (ELISA-2) using Murex version III kits (Murex Biotech Ltd, UK). All the anti-HCV positive samples were confirmed by Immunoblot assay, Chiron-RIBA-HCV 3.0 (Ortho clinical diagnostics, USA).
Six nephrologists, 38 staff nurses, and two HD technicians were directly involved in the patient’s care. All the personnel are regularly tested (once/ year) for anti-HCV/HBsAg and liver enzymes. No HD personnel resulted positive for HBV/ HCV at any stage in the study. Blood and the blood products used for transfusion were acquired from voluntary donors and screened for anti-HCV with ELISA-2.
Statistical analyses
All the quantitative variables were expressed as mean ± standard deviation (SD) and the statistical analyses were carried out using SPSS version 10.1 (SPSS Inc. Chicago, IL) software package. Comparison of the prevalence of anti-HCV positivity and seroconversion rates between reference (PC) group and other vascular access (AVF, PTFE graft and TC) groups were calculated by means of Chi square test with p-value of <0.05 being considered as significant.
RESULTS
Out of 198 ESRD patients, 86 (43.4%) with mean age of 65.0 ± 9.2 years, were found to be anti-HCV positive including 54 males and 32 females while the remaining 112 (56.6%) patients (53 males and 59 females) with mean age of 49.0 ± 5.8 years, were anti-HCV negative. Significantly higher mean age (p < 0.03) was observed among anti-HCV positive patients compared to those with negative anti-HCV serology (65.0 ± 9.2 vs 49.0 ± 5.8 years). A statistically significant relationship between the anti-HCV positive serology and the male gender (p < 0.04), was also observed, 62.8% (54/86) of the anti-HCV positive patients were males whereas only 37.2% (32/86) were females.
However, the number of units of blood transfused in anti-HCV positive and anti-HCV negative cohorts were comparable (7.2 ± 2.5 vs 6.8 ± 3.7 units) indicative of no significant relationship between anti-HCV positivity and the units of blood transfused. Likewise, a significant correlation (p < 0.002) between anti-HCV positivity and higher dialytic age was observed. An overall, HCV seroconversion rate of 8.6% per year was recorded in this HD cohort.
Among the patients with various types of vascular accesses, AVF group recorded significantly higher HCV prevalence of 61.7% (63/102) and seroconversion rate of 12.3% per year as compared to the lowest prevalence of 12.9% (4/34) and seroconversion rate of 2.5%, observed in the reference (PC) group (p < 0.0001). Patients dialyzed through PTFE grafts recorded next highest HCV prevalence of 47.8% (11/23) with seroconversion rate of 9.5% (p<0.016). On the other hand, TC group had statistically insignificant HCV prevalence of 19% (8/42) and seroconversion rate of 3.8% in comparison to those of the reference (PC) group (Tab. I).
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TABLE I
PATIENT CHARACTERSTICS AND HCV SEROLOGY IN HEMODIALYSIS COHORT (N=198)
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DISCUSSION
HCV is an emerging global public health concern with particular reference to the high-risk HD patients. The prevalence of anti-HCV positivity among HD patients remains high compared with that of healthy population. The HCV seroprevalence of 43.4% observed in this study is comparable to 43.9% reported from this region of the Eastern Province of Saudi Arabia (13). However, it is much lower than 72.3% reported from the Western Province and 68% in a multicenter epidemiological study carried out in Saudi Arabia (14, 15).
Frequently transfused HD patients have been reported to be at a greater risk of contracting HCV infection (5, 6, 14-18). However, our results do not link the acquisition of HCV infection with blood transfusion as the number of units of blood transfused between the anti-HCV positive and the anti-HCV negative groups were comparable (7.2 ± 2.5 Vs 6.8 ± 3.7 units). In addition, routine careful screening with highly sensitive HCV screening tests for blood donors (ELISA-HCV), the risk of post-transfusion HCV infection (< 1/100,000 blood units) is almost negligible (19).
Our study, like some others (5, 6, 15-18) clearly shows a significant relationship between the dialytic age and anti-HCV positivity. Patients with dialytic age of 50.0 ± 8.6 months carried significantly higher risk (p<0.002) of acquiring HCV infection than those with dialytic age of 29.0 ± 5.9 months. Dialytic age has been considered a powerful risk predictor of acquisition of HCV infection. The likelihood of acquiring HCV infection is considerably enhanced after a decade of HD with the reported predictable risk of 10% per year (10, 20).
Patient to patient transmission of HCV has been demonstrated through recent molecular biological studies, carried out in high prevalence HD units (21, 22). It occurs often through blood contaminated gloves and hands of HD staff, dialysis equipment, dialyzer and blood line surfaces (5-10). Sharing HD machines and reprocessing of dialyzers, have also been reported to play a role in the dissemination of HCV infection (2, 5, 6, 23). The disruption of the membrane integrity while reprocessing the dialyzers could possibly permit the passage of virus into the blood compartment (24, 25). In addition, the outbreaks of HCV transmission have been reported in HD units, due to failures to strictly enforce the universal precautions, for instance-failure to change gloves between the patients while performing HD treatments, especially during emergency situations (26).
An overall seroconversion rate of 8.6% per year observed at this tertiary care center is comparable to those of 7-9% reported from other HD centers of Saudi Arabia and elsewhere (2, 15). However, annual seroconversion rates of >5% per year, reported in HD units with >20% prevalence rates, continue to be the cause for concern (5).
The epidemiological situation of HD patients, who are treated in the units of high baseline HCV prevalence and who need access to the circulation three times per week, places them at substantial risk of exposure to HCV infection. The seroprevalence of antibody to HCV and seroconversion rate among patients dialyzed through AVF and PTFE grafts, were significantly higher than those dialyzed through PC (reference group). On the other hand, patients dialyzed via TC revealed no statistically significant difference in the HCV seroprevalence and seroconversion rates compared with reference (PC) group. These observations are indicative of the greater risk of HCV infection, in patients dialyzed through AVF or PTFE, than in those using vascular catheters. The breakdown in the infection control procedure against HCV is, likely to be responsible for the transmission of virus among HD patients; It is also probable that such a breakdown occurs more frequently in HD patients using AVF and PTFE grafts.
AVF and PTFE grafts, are both preferred forms of vascular access; however, their proper handling requires experience and skill, to gain access to circulation and achieve adequate blood flow for the extracorporeal circuit through regular punctures and cannulations, imperative to initiate HD. In addition, thumb pressure for few minutes is required to stop the bleeding from the vascular puncture sites, at the end of the procedure. Presence of HCV-RNA in the hand washing water of nurses dialyzing HCV positive as well as negative patients has been demonstrated in a recent clinicovirological study from the Middle East (27). Contamination of the vascular puncture sites could take place at some stage during handling of these accesses via nosocomial pathway through cross-infection mechanism, from the patients already infected.
Thus, the outcome of this study shows that patients with AVF and PTFE grafts, comprising > 60% of this high HCV prevalence HD cohort, are at much greater risk of acquiring HCV infection through nosocomial transmission than those dialyzed through vascular catheters. Difficult handling of the AVF and PTFE grafts could facilitate the accessibility of HCV to blood circulation, during initiation and/or termination of HD procedure. The procedure related transmission of HCV could be effectively prevented by rigorous application of universal precautions as recommended by CDC and possibly by strict isolation of HCV positive patients (28, 29). However, multicenter molecular follow-up studies with larger sample size, are required to corroborate these observations and to formulate appropriate strategies accordingly.
Reprint requests to:
Anil K. Saxena, MD
Division of Nephrology
King Fahad Hospital and Tertiary Care Center
Hofuf, Al-Hasa-31982
Saudi Arabia
e-mail: dranil_31982@yahoo.com
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A.K. Saxena
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