Cadaver donor discards secondary to serology

Screening algorithms for HBV, HCV, HIV and syphilis in an anatomical donation program

BACKGROUND

Users of anatomical donors are at risk of exposure to bloodborne pathogens. This study evaluated screening algorithms for hepatitis B and C virus, human immunodeficiency virus and Treponema pallidum during donor allocation and assessed the impact of postmortem time on hemolysis and how hemolysis affects test results and donor discard rate.

METHODS

From 2011 to 2018, demographic data of anatomical donors, time of postmortem blood sampling, presence of sample hemolysis, serological test results (negative; active infection; false reactive screening test; historic infection; inconclusive; technically impracticable) and the actual donor allocation were collected.

RESULTS

Donors (n = 537) had a mean age of 77.53 ± 13.67 (24-103) year. Nine (1.68%) had laboratory test results indicative for active infection for hepatitis B (n = 1) and C virus (n = 2), human immunodeficiency virus (n = 5) and T. pallidum (n = 1). Negative screenings ranged from 74.67 to 97.58%, depending on the pathogen. According to the original screening algorithms, 479 (89.20%) donors should have been accepted. In practice, a donor acceptance rate of 91.20% was found. Analysis of potential donor allocation interpretation obstacles resulted in simplification of the in-house laboratory testing algorithms and addition of a nucleic acid test to increase the reliability for identification of active (acute) human immunodeficiency virus infection. Hemolysis was more common when sampling was performed more than 24 h after death (p < 0.001). Hemolytic samples more frequently showed a reactive or indeterminate human immunodeficiency virus test result (p < 0.001). Screening for human immunodeficiency virus and T. pallidum was technically more impracticable when hemolysis was present (p = 0.042 and p = 0.003, respectively). Donors with hemolytic blood samples were more often discarded (46.88%) compared to bodies with non-hemolytic samples (6.32%) (p < 0.001).

CONCLUSIONS

Despite the implementation of donor screening algorithms, a significant number of bodies have an inconsistent allocation. New algorithms, to be evaluated in future research, were suggested. Early postmortem blood sampling is key as hemolysis can influence certain test results and donor allocation.

Skin substitutes for acute and chronic wound healing: an updated review

Background: Skin substitutes are designed to accelerate wound healing by providing replacement of extracellular matrix and can be used to promote healing of both acute and chronic wounds.Aim: To describe advantages, disadvantages, and indications for different skin substitutes with the intention of providing a systematic framework that clinicians can easily utilize in clinical practice.Materials and method: We conducted a PubMed, Cochrane Library, and company website search for publications using various search terms associated with skin substitutes.Results: Skin substitutes can be categorized as epidermal, dermal, and composite, depending on the skin component they contain, and further split into different categories depending on their composition and source of material, including xenograft, acellular allograft, cellular allograft, autograft, and synthetic skin substitutes. Because there is no ideal option for skin substitutes that meet all the criteria for optimal wound healing, there is ongoing research evaluating and developing different skin substitute options.Conclusion: Our model of skin substitutes was organized based on the different layers of cutaneous involvement and the origin of the product material. We believe that this framework provides a practical guide for selection of the most appropriate skin substitute based on clinical indication.

Advances in addressing full-thickness skin defects: a review of dermal and epidermal substitutes

full-thickness skin defects remain a reconstructive challenge. Novel regenerative modalities can aid in addressing these defects. A literature review of currently available dermal and epidermal regenerates was performed. The mechanism and application for each skin substitute was analyzed to provide a guide for these modalities. Available epidermal substitutes include autografts and allografts and may be cultured or noncultured. Dermal regenerate templates exist in biologic and synthetic varieties that differ in the source animal and processing. Epidermal and dermal skin substitutes are promising adjunctive tools for addressing certain soft tissue defects and have improved outcomes in reconstructive procedures. The following article provides a comprehensive review of the biologic materials available and the types of complex wounds amenable to their use.

A Comparative Examination of the Clinical Outcome and Histological Appearance of Cryopreserved and Fresh Split-Thickness Skin Grafts

The clinical use of frozen, human allogeneic skin grafts is considered a suitable alternative to freshly harvested allogeneic skin grafts when the latter are not available. However, limited functional and histological information exists regarding the effects of cryopreservation on allogeneic skin grafts, especially those across mismatched histocompatibility barriers. Thus, we performed a side-by-side comparative study of fresh vs frozen skin grafts, across both minor and major histocompatibility barriers, in a miniature swine model. Since porcine skin shares many physical and immunological properties with human skin, our findings have relevance to current clinical practices involving allogeneic grafting and may support future, temporary wound therapies involving frozen xenografts, comprised genetically modified porcine skin. Four miniature swine underwent harvest and grafting of split-thickness skin, with and without cryopreservation, in order to observe autologous grafts and grafts across minor and major histocompatibility barriers. A biopsy of the grafts was done at regular intervals for study of architecture, vascularization, and outcomes. All grafts vascularized without technical complications. Differences were noted in the early appearance of some fresh vs frozen grafts, but no significant difference was observed in overall survival times in any of the experimental groups. These results demonstrate that despite early observable differences in the healing process, cryopreservation and thawing does not significantly affect long-term graft survival or time to rejection, thus supporting the clinical and experimental use of fresh and frozen split-thickness skin grafts as comparable and interchangeable.

Genetically modified porcine split-thickness skin grafts as an alternative to allograft for provision of temporary wound coverage: preliminary characterization

Temporary coverage of severely burned patients with cadaver allograft skin represents an important component of burn care, but is limited by availability and cost. Porcine skin shares many physical properties with human skin, but is susceptible to hyperacute rejection due to preformed antibodies to α-1,3-galactose (Gal), a carbohydrate on all porcine cells. Our preliminary studies have suggested that skin grafts from α-1,3-galactosyltransferase knock out (GalT-KO) miniature swine might provide temporary wound coverage comparable to allografts, since GalT-KO swine lack this carbohydrate. To further evaluate this possibility, eight non-human primates received primary autologous, allogeneic, GalT-KO, and GalT+xenogeneic skin grafts. Additionally, secondary grafts were placed to assess whether sensitization would affect the rejection time course of identical-type grafts. We demonstrate that both GalT-KO xenografts and allografts provide temporary coverage of partial- and full-thickness wounds for up to 11 days. In contrast, GalT+xenografts displayed hyperacute rejection, with no signs of vascularization and rapid avulsion from wounds. Furthermore, secondary GalT-KO transplants failed to vascularize, demonstrating that primary graft rejection sensitizes the recipient. We conclude that GalT-KO xenografts may provide temporary coverage of wounds for a duration equivalent to allografts, and thus, could serve as a readily available alternative treatment of severe burns.

Porcine xenografts vs. (cryopreserved) allografts in the management of partial thickness burns: is there a clinical difference?

Porcine xenografts and cryopreserved allografts are used for the management of partial thickness burns and both biological materials have strong advocates with regard to clinical performance, the possibility of disease transfer from donor to recipient and other clinical aspects. A literature analysis was performed in an attempt to investigate whether true (statistically significant) differences exist on clinical performance and on other determinants for use. Comparing the results of this study with a similar, previously published study performed on possible differences amongst different types of allograft in the management of partial thickness burns, both allografts and porcine xenograft seem to perform equally well clinically with regard to healing related outcomes. In addition, the risk of disease transfer, in real life, was shown to be minimal. Consequently, clinical aspects being equal, other aspects such as price and availability should be used to decide which material to use for the management of partial thickness burns.

Advances in treating skin defects of the hand: skin substitutes and negative-pressure wound therapy

Surgeons and scientists have been developing alternative methods of hand reconstruction that may play an adjunctive role to, or completely supplant, more traditional reconstructive modalities. This article provides an overview of these emerging techniques, with an emphasis on skin substitutes and negative-pressure wound therapy as they apply to the treatment of soft tissue defects of the hand. The indications, contraindications, and relative advantages and disadvantages of these techniques are discussed in detail.

Preservation methods of allografts and their (lack of) influence on clinical results in partial thickness burns

Allografts, cadaver skin and amnion membrane are considered the golden standard in the management of partial thickness burns. However, debate on whether the tissue needs to be viable is on-going, since many believe that viable grafts result in better healing. The objective of this literature survey was to analyse the evidence on the method of preservation of allografts (cadaver skin or amnion membrane, glycerol, cryopreservation, lyophilisation) having a clinical impact on the healing of partial thickness burns. The survey focussed on preservation techniques and clinical outcomes (reepithelialisation) in partial thickness burns, as well as on differences in viability, immunogenicity and antimicrobial properties of the preservation methods. Most studies on allograft treatment of partial thickness burns are observational, with only one study of a (historical) comparative nature. A true meta-analysis was not performed and the results of this survey are observational in nature as well: they indicate that there is no evidence that viability of the graft influences healing outcomes. Thus, instead of viability, other aspects, such as intrinsic antimicrobial safety of the preservation method and cost should be the primary criteria for the choice of preservation method to be used for allografts.

Active wound coverings: bioengineered skin and dermal substitutes

Extensive skin loss and chronic wounds present a significant challenge to the clinician. With increased understanding of wound healing, cell biology, and cell culture techniques, various synthetic dressings and bioengineered skin substitutes have been developed. These materials can protect the wound, increase healing, provide overall wound coverage, and improve patient care. The ideal skin substitute may soon become a reality.

Phase I/II clinical evaluation of StrataGraft: a consistent, pathogen-free human skin substitute

BACKGROUND

Large wounds often require temporary allograft placement to optimize the wound bed and prevent infection until permanent closure is feasible. We developed and clinically tested a second-generation living human skin substitute (StrataGraft). StrataGraft provides both a dermis and a fully-stratified, biologically-functional epidermis generated from a pathogen-free, long-lived human keratinocyte progenitor cell line, Neonatal Immortalized KeratinocyteS (NIKS).

METHODS

Histology, electron microscopy, quantitative polymerase chain reaction, and bacterial growth in vitro were used to analyze human skin substitutes generated from primary human keratinocytes or NIKS cells. A phase I/II, National Institute of Health-funded, randomized, safety, and dose escalation trial was performed to assess autograft take in 15 patients 2 weeks after coverage with StrataGraft skin substitute or cryopreserved cadaver allograft.

RESULTS

StrataGraft skin substitute exhibited a fully stratified epidermis with multilamellar lipid sheets and barrier function as well as robust human beta defensin-3 mRNA levels. Analysis of the primary endpoint in the clinical study revealed no differences in autograft take between wound sites pretreated with StrataGraft skin substitute or cadaver allograft. No StrataGraft-related adverse events or serious adverse events were observed.

CONCLUSIONS

The major finding of this phase I/II clinical study is that performance of StrataGraft skin substitute was comparable to cadaver allograft for the temporary management of complex skin defects. StrataGraft skin substitute may also eliminate the risk for disease transmission associated with allograft tissue and offer additional protection to the wound bed through inherent antimicrobial properties. StrataGraft is a pathogen-free human skin substitute that is ideal for the management of severe skin wounds before autografting.

Prevalence of skin allograft discards as a result of serological and molecular microbiological screening in a regional skin bank in Italy

BACKGROUND

Postmortem skin is widely used in the treatment of patients with severe burns. Skin specimens must be screened for transmissible agents including human immunodeficiency virus (HIV), hepatitis B (HBV) and C (HCV) virus, human T-cell lymphotropic virus (HTLV), cytomegalovirus (CMV) and Treponema pallidum.

METHODS

Four hundred and sixty-one cadaveric donors underwent serological and molecular microbiological (polymerase chain reaction, PCR) screening at Siena Skin Bank between 2000 and 2004.

RESULTS

74/461 donors (16.1%) were found ineligible under current regulations.

CONCLUSIONS

These results are interesting in a local context and underline the importance of screening involving both routine serological procedures and molecular microbiological investigation. The latter has not been uniformly introduced in many countries and very limited data is available to assess its cost-benefit ratio in the field of skin donor screening.

Infective agents in fixed human cadavers: a brief review and suggested guidelines

Cadavers remain a principal teaching tool for anatomists and medical educators teaching gross anatomy. Infectious pathogens in cadavers that present particular risks include Mycobacterium tuberculosis, hepatitis B and C, the AIDS virus HIV, and prions that cause transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease (CJD) and Gerstmann-Straussler-Scheinker syndrome (GSS). It is often claimed that fixatives are effective in inactivation of these agents. Unfortunately cadavers, even though they are fixed, may still pose infection hazards to those who handle them. Specific safety precautions are necessary to avoid accidental disease transmission from cadavers before and during dissection and to decontaminate the local environment afterward. In this brief review, we describe the infectious pathogens that can be detected in cadavers and suggest safety guidelines for the protection of all who handle cadavers against infectious hazards.