Haemovigilance – Blood Safety

Kulsum International Hospital offers NAT Screened blood for all transfusions

HISTORY OF BLOOD TRANSFUSION

Blood transfusion is one of the historical achievements of mankind. History of efforts to transfuse blood dates back to early 17th century. Finally a successful human to human blood transfusion was first performed by James Blundell in 1818, since then the history of blood transfusion is full of the success stories. Discovery of blood groups, blood typing, cross match, establishment of blood banks, blood plasma transfusion, harvesting platelet concentrates, blood screening for viruses, and other live organisms are the major milestones. With the advancement in blood preservation and cross match techniques blood was thought safe till medical scientists discovered that if blood of a disease carrier is transfused to another person it can transmit disease to the recipient. A number of viruses, bacteria and other organisms can be transmitted through blood transfusion. Globally the surety of a blood clean of all harmful viruses, bacteria and other organisms was urged and a blood screening strategy was implemented to prevent the disease transmission.

SILENT CARRIERS OF DISEASE

In Pakistan, donor blood screening for Hepatitis B, Hepatitis C, AIDS, malaria, and syphilis is mandatory. Blood screening through a sensitive and reliable method must be ensured and preferred due to seriousness of the diseases transmitted. It is a fact that a person acquiring Hepatitis B, C or AIDS virus remains silent carrier for a long time and gradually falls sick. Just after the entry of a virus in body it is engulfed by the body’s defense mechanisms. The virus is either eliminated by defense system or it escapes and thrives in body. In case if it thrives  it can be detected either by appearance of its surface particles in blood called as antigens or by a protein produced against this antigen called as viral antibody.  Blood screening methods detect either antigen or antibodies (the method is called as immunological assay) which are produced after few weeks of infection, during this period the virus is present in body, the host is unaware and apparently without any sick feeling.  During this period the virus can be transmitted through blood to another person even if it is tested and found negative for these diseases and it is known as dark period or window period. These silent carriers transmit disease if they donate blood in this window period.

NUCLEIC ACID TESTING OF BLOOD

As it takes few weeks for antigens or antibodies to be detectable in blood by immunological methods, more sensitive strategies to detect viral genome in blood at very early stage (during window period) of infection were explored. Currently, the immunological methods are regarded as inadequate to ensure blood safety. The viral genome can be detected in blood within first week of infection with a sensitive method. The genome is made up of nucleic acids distinct for each species; this genomic detection in blood is called as nucleic acid testing (NAT). Globally the screening by NAT is regarded as most sensitive and appropriate for blood screening. It has been imposed mandatory for blood screening in USA, UK and other developed countries. In Pakistan it is at early stage and only few blood bank facilities screen blood by NAT methodology. This strategy almost eliminates the possibility of viral transmission through blood, fresh frozen plasma or platelet concentrate.

WHY SHOULD WE ENSURE NUCLEIC ACID TESTED BLOOD?

In Pakistan, Hepatitis B and Hepatitis C are endemic and danger of spread of AIDS is lurking. The true incidence of these diseases is not known due to non-availability of authenticated data, however most of the studies conclude 3-5% Hepatitis B and Hepatitis C each in general population and 1-3% each in apparently healthy blood donors. Past studies conducted in well reputed institutes of Pakistan show that a significant number of apparently healthy blood donors declared safe by screening with immunological methods may show evidence of viral genome when screened by NAT methodology. People receiving multiple transfusions as in case of cardiac surgery, major surgery, complicated child birth, Hematological disorders, accidental injuries and patients on dialysis are more at risk. Countries where the incidence of these viruses is < 1 in 100,000 consider NAT as a mandatory measure why we should not in Pakistan?  Kulsum International Hospital consider patient safety as its Core value and to meet its Corporate Social responsibility(CSR) has now decided that patients receiving blood which in addition to normal legal testing is also NAT tested to eliminate any chance of spread of these diseases through blood transfusion or its products.

REFERENCES

  1. WHO, 2017, Blood transfusion safety. [Online] Available at <http://www.who.int/bloodsafety/haemovigilance/en/> [Accessed at 01-Jan-2017].
  2. Stainsby D, Faber JC, Jorgensen J. Overview of hemovigilance. In: Simon TL, Solheim BG, Straus RG, Snyder EL, Stowell CP, Petrides M, editors. Rossi’s Principles of Transfusion Medicine. 4 th ed. West Sussex: Blackwell Publishing; 2009. p. 694.

By
Dr. Brig . Nadir Ali (Retd.)
(Haematologist)

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