Processing: donor testing

7 ASCP MLS practice questions on Processing: donor testing, part of Blood Banking. The first 7 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   Which donor test shortens the HIV window period compared with antibody testing?

   1. AWestern blot
   2. BALT
   3. CNucleic acid testing (NAT)
   4. DAnti-HBc

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   Answer: C · Nucleic acid testing (NAT)

   Nucleic acid testing detects viral RNA or DNA days to weeks before antibodies appear. Every US donation is tested by NAT for HIV-1, hepatitis C and hepatitis B. This has cut the residual risk of each of these infections to roughly one in a million units or lower. Antibody tests are still done alongside NAT.

   • A: The Western blot is a supplemental antibody test and has a longer window period than NAT.
   • B: ALT is a liver enzyme and is no longer required for donor screening.
   • D: Anti-HBc is a hepatitis B marker, not an HIV test.

2. Question 2 · Hard

   A repeat donor's HIV-1 NAT is positive on today's donation. Earlier donations from this donor were negative. What is 'lookback'?

   1. ATracing earlier donations so their recipients can be notified
   2. BRecalling and destroying only today's donation
   3. CRetesting today's unit after a 7-day hold
   4. DTesting the donor's sexual partners and family

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   Answer: A · Tracing earlier donations so their recipients can be notified

   Earlier donations may have been collected during the window period, before any test could detect the infection. Lookback finds those components, quarantines any still in stock and notifies the facilities that transfused them. The recipients' physicians then tell the recipients and offer testing. Lookback is required for HIV and hepatitis C.

   • B: Earlier donations may also be infectious, so stopping at today's unit is not enough.
   • C: Retesting today's unit does not protect people who received earlier donations.
   • D: Contacting the donor's partners is a public health task, not lookback.

3. Question 3 · Hard

   A donor is HBsAg nonreactive and HBV NAT nonreactive, but anti-HBc is repeat reactive. Why is the unit not transfused?

   1. AIt means the donor was recently vaccinated for hepatitis B
   2. BIt shows the donor is immune, so the plasma would neutralize the vaccine
   3. CAnti-HBc can mark a past infection with low-level virus that HBsAg tests miss
   4. DAnti-HBc reactivity is always a false positive

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   Answer: C · Anti-HBc can mark a past infection with low-level virus that HBsAg tests miss

   Antibody to hepatitis B core antigen follows real infection, never vaccination. Some people with anti-HBc alone have 'occult' hepatitis B, with small amounts of virus that HBsAg and NAT may miss. Anti-HBc testing therefore removes units that could transmit hepatitis B. Hepatitis B vaccine produces anti-HBs only.

   • A: Vaccination produces anti-HBs, not anti-HBc.
   • B: Immunity is not a reason to discard a unit, and plasma does not affect vaccines.
   • D: Anti-HBc can be a false positive, but it often reflects a real past infection.

4. Question 4 · Medium

   Which test or safety step is needed for platelet components but not for red cells before release?

   1. AABO grouping and Rh typing of the unit
   2. BAntibody testing for HTLV-I and HTLV-II
   3. CNucleic acid testing for HIV-1
   4. DBacterial testing or pathogen reduction

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   Answer: D · Bacterial testing or pathogen reduction

   Platelets are stored at 20 to 24 °C, where contaminating bacteria can grow quickly. FDA guidance therefore requires a bacterial risk control strategy for platelets: culture, rapid testing or pathogen reduction. Septic reactions from platelets used to be the most common infectious risk of transfusion. Red cells are stored cold, so the risk is much lower.

   • A: ABO and Rh typing is done on every donation.
   • B: HTLV testing is done on all donations, not only platelets.
   • C: HIV NAT is done on every donation.

5. Question 5 · Medium

   Which donor screening test needs to be done only once per donor, if the first result is negative?

   1. AAntibody to Trypanosoma cruzi
   2. BHIV-1 nucleic acid test
   3. CAntibody to hepatitis C virus
   4. DHepatitis B surface antigen

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   Answer: A · Antibody to Trypanosoma cruzi

   FDA allows one-time testing for antibody to Trypanosoma cruzi, the cause of Chagas disease. New infections in the United States are very rare, so retesting the same donor adds little. HIV, hepatitis B and hepatitis C markers are tested on every donation. Donors with a positive T. cruzi test are deferred indefinitely.

   • B: HIV NAT is required on every donation.
   • C: Anti-HCV is required on every donation.
   • D: HBsAg is required on every donation.

6. Question 6 · Medium

   A donor sample is initially reactive for anti-HCV. It is retested in duplicate: one result is reactive and one is nonreactive. How is the unit handled?

   1. ARelease it, because one repeat test was nonreactive
   2. BTreat it as repeat reactive: discard the unit and do supplemental testing
   3. CRun a third test and release the unit if it is nonreactive
   4. DUse it only for plasma fractionation

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7. Question 7 · Hard

   A 23-year-old first-time donor gives whole blood at a college drive. His donor screening results: HBsAg repeat reactive and confirmed by neutralization; total anti-HBc nonreactive; HBV DNA reactive by individual-donation NAT; anti-HCV and HCV RNA nonreactive; anti-HIV-1/2 and HIV-1 RNA nonreactive; anti-HTLV-I/II nonreactive; treponemal syphilis assay nonreactive. Two days after donating he phones the center to report fatigue and nausea. He reports no earlier hepatitis and no transfusions. What do these results show, and how is the donor managed?

   1. ARecent HBV vaccination; he may return later
   2. BOccult HBV infection; defer him indefinitely
   3. CChronic HBV infection; defer him indefinitely
   4. DEarly acute HBV infection; defer him indefinitely

   Answer and explanation in LearnFree account