الفهرس 
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Abstract
Among the well known transfusion-associated risks, the transmission of pathogenic viruses is regarded as one of the most serious. Over the past two decades, a series of overlapping safety procedures have been successively implemented to minimize this risk. It is now generally considered that the risk of transmitting viral infections via blood products is very low in developed countries.
The frequency of an infectious donation entering the blood supply may be due to the window period, assay failures and human and technical errors in testing and processing. The window period risk was estimated using the incidence of infection in donors and the length of the window period for tests in use, with an adjustment for atypical inter-donation intervals in seroconverting donors.
Successes in preventing transmission of viral infections during the last 10 to 20 years have led to very low incidence rates and estimated residual risk for transfusion-transmitted viral infections . This reduction was primary achieved by a careful medical selection of the donors, improved sensitivity of serological tests and the introduction of NAT in mini-pools for HCV and HIV.(215)
The main aim of introducing NAT in blood testing was the reduction of the residual risk of viral transmission linked to the window period. Each country bases the residual risk estimate on the mathematical model developed by Schreiber et al (216) which takes into account the window period and the incidence rate calculated from seroconversions observed in the repeat blood donor population..
The aim of the present study was to evaluate the residual risk of HCV transmission through blood donation and the possible role of ALT in minimizing the risk of transmission..
Blood donors were tested for Anti-HCV antibodies by ELISA test and classified into three groups:
Group (I) included 21 blood donors with O.D. of the ELISA test around cut off.
Group (II) included 84 anti-HCV negative blood donors and tested for ALT. An additional third group(III) was added including 39 blood donors with O.D. of ELISA around cut off and tested by pooling their samples ( 3 – 6 samples)
Blood samples were collected from all blood donors for further investigation .
1- Detection of HCV-RNA by real time PCR.
2- Detection of ALT by Randox.
In the present study, group I ( 21 blood donors with anti-HCV around cut off) was tested by real time PCR for HCV-RNA., 4 (19 %) out of the 21 blood donors had a low viral load ranging from 4.5 x102 - 2.8 x103/ml , and only one blood donor with a viral load of 1.3 x103 iu/ml showed mildly elevated ALT.
On the other hand, In group (II) the 84 anti-HCV negative blood donors were tested for ALT. 5 out of 84 anti-HCV negative blood donors had elevated ALT levels with values ranging from (50 -79 U/l ) and were found to be HCV-RNA negative by PCR. 39 blood donors of group (III) were pooled ( 3-6 samples) and were tested for HCV-RNA by PCR. Only one out of the 10 pooled sample was found to be positive for HCV-RNA.
In conclusion it was found that , the use of ALT level as a surrogate marker would not be of much benefit since only one (25%) out of the 4 HCV-RNA positive blood donors had mild ALT elevations and also 5 (5.9 %) out of 84 anti-HCV negative had elevated ALT levels ranging from (50-79 U/l) . All of them were negative for HCV-RNA
Dental manipulation has the most relevant impact on HCV infection followed by surgery.
The size of the pool of the blood samples must be optimized if NAT to be adopted in Egypt to reach the best cost effectiveness of the test.