Wednesday, 21 January 2009

Blood Transfusion and Hepatitis B....Concluded

The articles related to blood transfusion and hepatitis B infection have been published in three installments earlier and now being concluded. Any one interested to get any such article written as this may write to kamalkali1962@yahoo.com.

A critical evaluation the laboratory tests that are available for testing blood donations for the presence of anti-HBc.


Among anti-HBc assays there are nine assays which are used by the laboratories across the world. These nine assays are divided into two groups; competitive and non-competitive. The competitive assays are Murex, AxSYM, PRISM® HBcore, PRISM® HBc, COBAS Immulite and the non-competitive assays are ADVIA and Ortho. The choice of assays depend upon the suitability of its use varies from one medical community to other and the cost factors matter too. However, in case blood transfusion, with its social objectives in mind, most of the developed and developing nations opt for those assays which are cost effective and dependable.
The prevalent tests used to determined anti-HBc, can detect a small percentage of donors with false positive results. This is hazardous and anti-HBc (IgG and IgM) tests are available commercially since 70s and around 25 licensed commercial tests are available in the market and most of them are competitive in format. They all use HBcAg recombinant alike coupled to solid phase with variations are given by different HBcAg antibody like human, mouse-monoclonals etc, adding of reducing agents and taking different system of detection like enzymes, fluorescence, chemiluminescence, radiotracers etc. Different incubation procedures influence the kinetics like temperature, time and incubation steps. All the manufacturers claim sensitivity and diagnostic specificity to be higher than 99 per cent. Though studies found different kits produce divergent results (Caspari, Beyer, Elbert, Koerner, Muss, Schunter, Uy, Gerlich, Thomssen, Schmitt. 1989). However samples that show reactivity nearing cut-off are often likely to give false positives results. All over the world it is generally agreed that there should be a international criteria that is required to be applied to the donors for determining if there is true need and distinct benefits of such anti-HBc screening or maintaining of anti-HBc screening. There are several factors are required to be taken into consideration, direct and indirect both. The financial cost factor for the additional test, the additional number of staffs and equipments required to perform the test. The other pressure on blood transfusion service like expectations of unobtainable total safe blood and at the same time the pressure on the facilities like laboratories for another test, all merit consideration. There are more crucial issues as well; loss of donations and the donors by false result interpretation and poor specificity. Another fact is; the presence of anti-HBc also speaks of immunity to HBV. The test is necessary to determine to discriminate “anti-HBc alone” from immune response to HBV, so anti –HBs tests are required to be undertaken. So as the donors found anti-HBs (+)ve above certain level, though the specific level is yet to be agreed upon internationally, should be considered as immune to HBV, so they are healthy donors However with anti-HBc test being cleared by donors ; the transfusion of safe blood is mostly ensured.


Choice of the most appropriate test, justifying choice.


In a blood transfusion center the utmost cares are required to be taken to ensure that no transfusion transmitted disease spread through transfusion. The donors are donating their blood for saving others lives and inadvertently spread diseases jeopardizing the cause are tragic. So, detecting antibody to hepatitis B virus core antigen is a essential, so the new test for detecting anti –HBc presence in donor’s blood for ensuring the safe blood transfusion. While introducing and implementing new tests, keeping the key factors like cost, laboratory facilities, manpower and time; my best choice is the Ortho HBc ELISA Test System. The Ortho HBc ELISA Test system has been evaluated for determining its ability by Microbiological Diagnostics Assessment Service (MIDAS) (Rachel, Keith.2003). It has been evaluated and stated that the ORTHO HBc ELISA Test system ranks the fourth most sensitive anti-HBc assay and it has preferred determinant role in testing algorithm of HBV confirmation and distinguish HBsAg (+)ve specimens; so as to determine whether hepatitis B virus infection is current or past. The detection of anti-HBc alone or the reactivity shows a diminishing antibody response in a past infection but when the infection is at high titre, this may be due to chronic HBsAg being carried before the emergence of anti-HBs. In such cases the blood of the donor may be infectious (Grob,Jilg, Bornhak et al 2000: Alhababi, Sallam, Tong.2003). The Ortho HBc ELISA Test system and its effectiveness has been compared with other system as well and the result of these has been published in MHRA evaluations (White, Delieu, Perry, Parry.2003: White, Perry, Parry. 2003). The assays aware evaluated with same sera specimens and the kit has been appreciated. It is stated in the report by Rachel & Keith of MHRA that “the overall sensitivity of the ORTHO HBc ELISA Test System was 97.85 for the anti –HBc IDU specimens and was ranked overall as the fourth most sensitive anti-HBc assay evaluated. The ORTHO HBc ELISA test System could have a role in HBV confirmatory testing algorithm, further to characterize HBsAg positive specimens and to assist in determining whether HBV infection is pas or current. In many countries anti-HBc assays are used to screen blood donations. In this evaluation the ORTHO HBc ELISA Test System had a specificity of more than 99% and would therefore be a good candidate for blood screening” (Rachel, Keith.2003).


Discussion on how to implement this test, considering the impact of this test across the whole Blood Service with practical details as well as responses to the results.


The blood transfusion in health care system has a social objective that is to save the precious life. Implementation of a new test to ensure the supply of safe blood to recipients is a social, ethical and human mission. Though the blood donation is voluntary like organ donation, but the donor volunteers with a missionary zeal and this is true for all the donors. Anyone associated with medical professions or health care and the general public with awareness well appreciate the necessity of total safe blood transfusion. Unfortunately that remained unobtainable so far to the extent of cent percent because of the standard tests performed with the donor’s blood fail to ensure it. The incidence of transfusion transmitted diseases is not unfound of. Though the rate of such incidence; varies from one country to other, one ethnic group to other. The morality rate due to such incidence though not alarming in developed and developing nations, but it can still be downsized further. Ensuring donor’s blood free from hepatitis B virus is likely to take few steps ahead further towards the goal of safe blood transfusion. This is evident with the results found in countries like US and Germany where such additional tests are carried out for transfusion or blood or organs.
Hepatitis B virus infection was detected decades ago for being transmitted through blood transfusion. Except US and Japan other countries could not implement anti-HBc testing for several reasons (Busch.1998: . Kleinman, Busch .2001). The published data has ignored the anti- HBc-positive units, so as a percentage of HBc positive confirmed by HBV DNA detections has never been highlighted. However the hazards existed and the persons belonging to medical and health care facilities were well aware of it. Now, HBsAg assays being available with more sensitivity, so many countries and the local group performing anti-HBc tests like Japan and Germany. The results are encouraging and evident enough for highlighting the arrest of spreading transfusion transmitted diseases as per their data. So, this evidence is convincing enough to implement a new test for anti-HBc positive detection for transfusing safe blood and arrest the spread of transfusion transmitted diseases. The writer as a manager of blood transfusion facility would not find any problem to implement the new test by convincing the staffs as well as donors.


Conclusion

In the light of above discussion necessarily of the implementation of a new test for detecting anti-HBc positive for blood donors ensuring to arrest the spread of transfusion transmitted diseases has been well explained. The donors and the recipients both will be interested for the implementation of such test. Albeit at a little extra cost; after all no one likes to jeopardize the very mission of transfusion or transplantation by allowing the transfusion transmitted diseases hazard the human life.


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