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Saudi Journal of Kidney Diseases and Transplantation
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LETTER TO THE EDITOR  
Year : 2012  |  Volume : 23  |  Issue : 1  |  Page : 138
Eliminating the chronic problem of false positive HCV testing from hemodialysis units at lowest cost


Consultant Nephrologist, King Fahd Specialist Hospital, Dammam, Saudi Arabia

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Date of Web Publication3-Jan-2012
 

How to cite this article:
Abutaleb N. Eliminating the chronic problem of false positive HCV testing from hemodialysis units at lowest cost. Saudi J Kidney Dis Transpl 2012;23:138

How to cite this URL:
Abutaleb N. Eliminating the chronic problem of false positive HCV testing from hemodialysis units at lowest cost. Saudi J Kidney Dis Transpl [serial online] 2012 [cited 2019 Jul 22];23:138. Available from: http://www.sjkdt.org/text.asp?2012/23/1/138/91321
To the Editor,

I discussed in an earlier published letter to the Saudi Journal of Kidney Diseases and Transplantation (SJKDT) the limitations of HCV-ELISA tests. Several reasons may explain the finding of higher false negative results among patients on hemodialysis (HD). Hemodialysis patients are relatively immunocompromised and thus, have a lower and a later antibody response to acute HCV infection. Window periods prior to seroconversion are longer and at times, are even permanent.

As such, the high rate of false negative HCV-ELISA results among patients on HD has practically resulted in failure of HCV isolation policies in HD units. I had suggested earlier adding a periodic NAT testing on a minipool blood sample collected from all the HCV-negative patients in each shift. Such minipool blood sample is to be collected from 10 to 25 patients and run with the routine, periodic HCV serology testing. Such NAT testing on a minipool blood sample is done to screen blood donors and should prove efficient to detect occult HCV infection among the HCV negative dialysis patients. The discussion made then was that the sensitivity of NAT is unlikely to be affected by such sample dilutions. It will practically eliminate the problem of hidden HCV infection among the dialysis patients who are late or completely unable to mount HCV antibody response.

The recently introduced quantitative HCV core Ag immunoassay, The ARCHITECT HCV Ag assay by Abbott, seems a very promising practical alternative to the NAT testing. The test has less than 20% of the cost of NAT with almost the same sensitivity, specificity and ability to detect the virus antigens almost within one day of the infection. The ability of the test to detect a viral load of 100 to 300 copies/mm 3 would allow detection of a positive result despite significant dilutional effect of pooling 10-20 blood samples together. The test has apparently become available in Europe and Asia although periodic utilization of the test on minipool samples from HD units has not been suggested earlier.

At any time, if minipool- HCV core Ag immunoassay testing is reported positive, it would suggest the presence of false negative HCV-infected patient(s) among the tested group. If not detected by the simultaneously carried out ELISA test, then HCV core Ag immunoassay or NAT test needs to be repeated on all the individual patients in the minipool group. By this approach, the false negative results can almost completely be eliminated at a lowest cost. Being much cheaper than NAT testing, the HCV core Ag test can also be carried out on individual patients or patient-groups (mini-pooled samples) returning from "holiday dialysis" with prompt and accurate results.

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Correspondence Address:
Nasrulla Abutaleb
Consultant Nephrologist, King Fahd Specialist Hospital, Dammam
Saudi Arabia
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PMID: 22237238

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