CTBS Tissue Processing & Preservation 3 — Questions and Answers
Question 1: Which solution is most widely used for short-term hypothermic preservation of vascular allografts awaiting processing?
- Normal saline (0.9% NaCl)
- University of Wisconsin (UW) solution (Correct answer)
- Phosphate-buffered saline (PBS)
- Lactated Ringer's solution
Correct answer: University of Wisconsin (UW) solution
UW solution contains impermeants, antioxidants, and buffers that minimize cell swelling and metabolic injury during cold ischemia.
Question 2: What is 'chondrocyte viability' most commonly assessed by in cartilage allografts?
- Hematoxylin and eosin (H&E) staining
- Live/dead fluorescent dye exclusion assay (Correct answer)
- Gross visual inspection
- Radiographic density measurement
Correct answer: Live/dead fluorescent dye exclusion assay
Live/dead fluorescent assays using calcein-AM (live) and ethidium homodimer (dead) dyes provide quantitative assessment of chondrocyte viability.
Question 3: Solvent/detergent (S/D) treatment of allograft tissue primarily inactivates which class of pathogens?
- Bacteria
- Enveloped viruses (Correct answer)
- Non-enveloped viruses
- Bacterial spores
Correct answer: Enveloped viruses
S/D treatment disrupts lipid envelopes of viruses (such as HIV and HBV) but does not effectively inactivate non-enveloped viruses like parvovirus B19.
Question 4: Which AATB standard specifies the minimum acceptable residual moisture content for lyophilized tissues?
- Greater than 6%
- Less than 6% (Correct answer)
- Exactly 12%
- Between 8–10%
Correct answer: Less than 6%
AATB standards require residual moisture of less than 6% in lyophilized tissues to prevent microbial growth and degradation during ambient storage.
Question 5: A tissue bank uses peracetic acid (PAA) as a terminal sterilant. Which tissue type would be LEAST suitable for PAA treatment?
- Cancellous bone chips
- Viable corneal endothelium (Correct answer)
- Tendon allografts
- Demineralized bone matrix
Correct answer: Viable corneal endothelium
PAA is an oxidizing agent that denatures proteins and destroys cell viability, making it incompatible with tissues intended to contain living cells.
Question 6: What is the maximum cold ischemia time generally accepted for fresh osteochondral allograft processing?
- 4 hours
- 24 hours
- 72 hours (Correct answer)
- 28 days
Correct answer: 72 hours
Most tissue banks target recovery-to-processing within 24–72 hours for fresh osteochondral grafts to maintain adequate chondrocyte viability.
Question 7: Which antibiotic combination is commonly used in tissue decontamination cocktails for musculoskeletal allografts?
- Penicillin, streptomycin, and amphotericin B (Correct answer)
- Ciprofloxacin and fluconazole only
- Vancomycin and amikacin only
- Clindamycin and metronidazole only
Correct answer: Penicillin, streptomycin, and amphotericin B
Broad-spectrum antibiotic/antifungal cocktails including penicillin, streptomycin, and amphotericin B address gram-positive, gram-negative, and fungal contamination.
CTBS Tissue Processing & Preservation 3
Which solution is most widely used for short-term hypothermic preservation of vascular allografts awaiting processing?