Three-tier screening process can stop HIV contamination, doctors say [Archives:2007/1100/Health]

November 5 2007

Robert Drapper
For Yemen Times

In the past, blood transfusions in Yemen were plagued by poor screening, and as a result, patients were infected with HIV. However, a new three-tier screening process comprised of the ELISA test, the Western blot and the Polymerase Chain Reaction (PCR) test has changed the way blood transfusions are handled in Yemen.

ELISA machines test blood samples for HIV, Habituates B, C and other infectious diseases. “It's very sensitive to infectious disease,” says Dr. Arwa Ahmed Awn, a Ph.D. in hematology, and blood transfusion and general director of Yemen's National Blood Transfusion and Research Center. Hematology is the diagnosis, treatment, and prevention of diseases of the blood and bone marrow as well as blood clotting and vascular systems. “Because of the nature of blood, the science of hematology profoundly affects the understanding of many diseases,” like HIV according to Webster's New World Medical Dictionary.

“Now every unit of blood is screened,” says Dr. Sa'eed Al-Sheibani, assistant professor at Sana'a University and general manager of Yemen's National Center of Public Health Laboratories. “If blood tests HIV-positive with the ELISA test, next is the Western blot and then the PCR,” Al-Sheibani explains.

The Western blot is the second step in confirming a positive HIV test confirmed by ELISA. According to registered nurse and HIV/AIDS specialist Mark Cichocki, “Western blot is a test for specific antibodies to confirm repeatedly reactive results of the HIV ELISA or EIA test.”

Once a blood sample has been subjected to the Western blot test, the sample will be either positive or negative. “A positive Western blot confirms HIV infection,” Cichocki explains. Next, is the PCR test, which tests for the (RNA) Ribonucleic Acid, of the HIV virus. RNA is a nucleic acid molecule similar to

DNA but containing ribose rather than deoxyribose. RNA is formed upon a DNA template.

According to, “The PCR test is 100 percent effective. There's no way you can get a negative result,” because the actual building blocks of the HIV virus are searched and confirmed in the blood sample provided. “PCR is a key technique in molecular genetics permitting analysis of any short sequence of DNA (or RNA) without having to clone it.”

Yemeni truck driver Mohammed Akhmed, 26, is one of many who donate blood “because I want to give to patients,” he says, believing that God will bless him for it. His friend, 29-year-old soldier Khalid Saad Al-Jaef, shares his sentiments in receiving blessing from God. “The person who receives my blood is my friend,” Al-Jaef says.

It's loving, caring blood donors like these who “give only for the blessing. They don't give for money,” says Dr. Ismail Akhmed Al-Radamy, “They think that if they give blood to patients, Allah will bless them.” It's this blessing and others like it that will be subjected to the ELISA test, which is mandatory.

Not all blood donations are subjected to the three-tier screening process. If a blood sample tests negative for HIV in the ELISA test, then no other test is needed. Only those ELISA tests that are HIV-positive are subjected to the Western blot and PCR test. Most blood that's HIV-positive is contaminated with the “SEARO HIV strand, which comes from different parts of Africa,” Dr. Sa'eed Al-Sheibani explains.

“It's very rare that we get positive results,” from donor cases, Al-Sheibani explains, “approximately 10 cases annually,” he says, noting that the public health lab receives approximately 60 donors each day.

All blood confirmed to be HIV-positive is associated with identification information specific to that donor. In the rare case that a donor at the public health lab tests positive for HIV, his or her information packet is sent directly to Al-Sheibani. “We then take them (the HIV-positive individual) to a committee, which educates them (him/her) about HIV,” Al-Sheibani explains.

HIV positive blood that's screened via the three-step process either is thrown away or used for scientific purposes.

“We deep-freeze the HIV-positive sample, storing it with the serial number, examination date and type of test. We keep the sample for research purposes or to test new procedures or diseases,” explains Dr. Abdullah Al-Hababi, who holds a master's in virology.

Finally, when it's time to dispose completely of HIV-infected blood, such biological waste and medical laboratory products are placed into an autoclave machine to sterilize them before incineration.

According to Dr. Al-Aiman Adel , it's this rigorous screening process that confirms HIV-infected blood and prevents some 20 cases of patients receiving blood transfusions monthly from becoming infected with HIV.