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Some doubts cast on hepatitis C tests of corneal donors
Evidence is lacking that screening tests actually detect hepatitis C in donor tissue.
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NAHARIYA, Israel – Current testing for hepatitis C virus may be inappropriate in some circumstances, according to a physician here.
“Food and Drug Administration guidelines concerning the rejection of corneas from HCV seropositive corneal donors should be reconsidered before instantly adapting these guidelines in all countries,” said Uri Rehany, MD, FACS, chairman of the department of ophthalmology at Nahariya Medical Center here.
Of the donor corneas rejected for transplantation, the largest group comes from donors testing seropositive for the hepatitis C virus (HCV). Although to date there have been no reported cases of HCV transmission by corneal transplantation, neither has there been any reported cases of HCV seropositive corneal donors in whom HCV RNA was detected in their corneas.
These data raise some doubts on the value and validity of the HCV serologic screening tests for corneal transplantation, Dr. Rehany said. The prevalence of HCV seropositivity may be significantly higher in developing countries in comparison to western countries. So, adapting the FDA guidelines for the selection of donor corneal tissue based on serologic screening tests would only waste large amounts of donor corneas that most probably are free of the HCV genome and suitable for transplantation. This would be significant in a situation of severe shortage in the supply of donor corneal tissue.
Dr. Rehany conducted research to find a simple, reliable and cost-effective method to detect the HCV antigen in the donor corneal button rim. The goal was to find a way to safely transplant some of the corneal tissue rejected only because it is HCV seropositive.
Dr. Rehany presented the results of his study, “The expression of HCV antigen by immunohistochemical and PCR methods in corneas of seropositive donors,” at the International Congress of Ophthalmology meeting in Sydney, Australia.
Unreliable tests
Dr. Rehany created a study to investigate the reliability, sensitivity and specificity of the immunohistochemical method for detection of HCV antigen in the donor corneal button and correlate it to the polymerase chain reaction (PCR) method.
Although PCR is a highly sensitive and specific technique for direct detection of HCV-RNA, it is not applicable for routine clinical use in most medical centers due to its unavailability, complexity and cost. While the immunohistochemical method cost for one donor cornea is about $4, the cost for the PCR method for one cornea may exceed $60, or 15 times the cost.
To correlate the detection of HCV antigen by immunohistochemical and PCR methods for the presence of HCV antigen in their corneal tissues and sera, researchers examined eight corneas of four seropositive corneal donors and eight corneas of four seronegative corneal donors. HCV-RNA was not detected in the sera and corneal tissues of any seropositive and seronegative corneal donors by either PCR or immunochemistry.
In a clinical setting, HCV is usually not detected in the corneal tissue but by serologic analysis of the cadaver donor blood, which has a 3% rate of false positives.
“Also, seropositivity does not mean that the corneal tissue is infected by HCV. We may assume that most of the rejected donor corneal tissue is HCV-free,” Dr. Rehany said.
According to the current FDA guidelines, negative serologic screening tests are required for HCV before release of the donor cornea for transplantation. However, to date, there have been no reported cases of HCV transmission by corneal transplantation, and there have been no reported cases of HCV seropositive corneal donors in whom HCV-RNA was detected in their corneas.
“Seropositivity for HCV may persist long after the active viral infection clears, causing the rejection of donor corneal buttons who do not contain infectious virus. There is no doubt that serologic tests of the donor blood are unreliable for the decision of the possible HCV infectivity of the corneal button,” he said.
Demand for tissue
This conclusion comes at a time when the supply of donor corneas for transplantation is remarkably insufficient all over the world, especially in developing countries where blindness due to corneal reasons is high, Dr. Rehany added.
“Extreme efforts must be made to save any corneal tissue that is suitable for transplantation. The rejection of so many high-quality donor corneas just because the donor was seropositive is unjustified. The release of corneal tissue for transplantation should be based, in my opinion, on a direct HCV detection test on the corneal tissue, proving it to be virus-free.”
However, more research is needed before implementing this on a wide-scale basis. The immunohistochemical method for detection of HCV antigen in a small piece of donor corneal rim may be a feasible and cost-effective method for the possible release of corneal tissue from seropositive donors for transplantation, though it is too small to be conclusive.
“I may advise that corneas taken from HCV seropositive donors may be transplanted once the tissue has been proven to be virus-free by some reliable and sensitive tests as suggested in the study,” Dr. Rehany concluded.
For Your Information:
- Uri Rehany, MD, FACS, can be reached at the Department of Ophthalmology, Western Galilee–Nahariya Medical Center, Nahariya 22100, Israel; +(972) 4-91-07-635; fax: +(972) 4-91-07-611; e-mail: rehany@naharia.health.gov.il.