In the most recent webinar on management of research animals sponsored by the NIH Office of Laboratory Animal Welfare (OLAW), Debra Hickman, director of the Laboratory Animal Resources Center at Indiana University (IU), discussed the concept of “humane endpoints.” These can be added to animal protocols to alleviate, as she put it, “any potential suffering that happens in that window between morbidity and mortality.”
In introducing Hickman, Susan Silk, OLAW director of policy, noted that Hickman “directs an active laboratory that explores how the biomethodology, handling, and housing selections that are used in research affect the well-being of animals used in research.” This is in addition to her clinical and administrative duties.
Hickman said it might be “fair” to consider replacing “endpoints” with humane endpoints in protocol applications.
Such a change might clarify “what it is that we’re asking” and differentiate for scientists who think “an end point is [only] the end of the study” occurring, for example, when data collection is complete or at 90 days when the animal is planned to be euthanized, she said.
Under the concept of humane endpoints, “What you’re asking is…when are we going to euthanize before your actual endpoints? So your protocol form needs to ask for the timeline of the study, which will get to the study endpoint in an experimental design, but you do need to ask [scientists] about their humane endpoints,” Hickman said during the Sept. 20 webinar.
When a humane endpoint is reached in an animal study, it marks the “time to remove the animal from the study,” Hickman explained.
Humane endpoints should be “clearly defined before any animal work starts,” she said.
“The last thing that we want is a situation where an animal is in distress or needs attention, and we’re not clear on what the path is,” triggering arguments between the scientist, the institutional animal care and use committee (IACUC) and veterinarian “over whether this animal has reached the agreed humane endpoints or not,” Hickman said. “That potentially can result in significant pain or distress for the animal. And so having all this in place before the study even starts is the best practice for making sure that we’re doing the best by the animals.”
Collaborative Approach Essential
Hickman pointed out that identifying humane endpoints might be a new idea for investigators, IACUCs, and veterinarians, or they may be applying them to a species they’ve never used before. As a result, “there may be contention around the decision of what the appropriate humane endpoint should look like,” and it may be useful to “bring in outside subject-matter experts to help with additional information.”
This may be helpful, “especially if you’re dealing with a [study] model that’s fairly complicated, involved [and] potentially has a lot of pain or distress for the animal…to make sure that you’re minimizing that pain and distress as you develop the intervention plan and the humane endpoints,” she said.
Said Hickman, “[D]eveloping appropriate humane endpoints is very study-dependent. Unfortunately, there is no ‘magic bullet,’ perfect solution that fits all cases, though there are tools that can have more universal application.” She expressed confidence that “if the researcher, the IACUC, and the veterinary staff work together, they can put together a plan that anticipates potential complications and develops a plan for intervention if and when those complications arise.”
Moreover, the plan for humane endpoints will address, “if those complications arise, how will they be identified and what will happen? Will they be a trigger for supportive care? Will they indicate that it’s time to remove the animal from the study? Will they indicate that it is time to euthanize the animal?” Hickman asked.
According to Hickman, “It’s critical for the IACUC, the researcher, and the veterinarian to look at the [research] model that’s being done, understand the model, and make sure the endpoints are appropriate for the model that is being used.”
Hickman emphasized that “one should never make decisions based on a single criterion. Ideally, the endpoint assessment, if it is a true well-being assessment, will include multiple components.”
In describing the primary factors when developing humane endpoints for studies, Hickman cited “really understanding what’s happening to the animal” being used in the research.
“I think one of the biggest pitfalls I see with my IACUC is that sometimes our scientists will just throw the generic endpoints in,” said Hickman. Weight loss or unthriftiness (being unhealthy) “may be appropriate, but they may not be.”
At the time of protocol review, the IACUC and scientist should discuss “what’s happening, what’s expected, what complications are expected,” as well as the frequency of monitoring and red flags, “so you can identify when those complications arise,” she said.
Examples of generic endpoints include the following:
◆ “Weight loss
◆ Inability to ambulate
◆ Labored respiration
◆ Dehydration
◆ Hunched posture
◆ Poor coat (piloerection)
◆ Wounds or hair loss
◆ Ocular or respiratory discharge
◆ Inability to access food or water”
Novel tools are available to “assess animal well-being in the context of humane endpoints. However, as much as possible, the criteria should be specific and objective and include behavioral and physiologic assessment[s],” Hickman said.
In addition, “there should be clear agreement of what score, generally a compilation of various individual assessments, or what specific criteria will trigger what action.”
At IU, officials search the literature “quite a bit to look to see if there’s been anybody who has found markers in a similar model that might be predictive of impending death,” Hickman said.
There is “evidence that in some infectious disease models, for example, as you see a decline in temperature, that correlates very strongly to death is coming,” Hickman said. “And so you can reasonably predict that when the animal’s temperature drops and they have achieved that level of morbidity, that they will be dying soon and you can euthanize them,” thus alleviating “any potential suffering that happens in that window between morbidity and mortality.”
But, she added, the literature also may show “a predictive parameter is not defined yet,” and point up the need for additional study.
Other tools include body condition score—comparing an animal’s ethogram to what is normal.
Regarding specific types of studies, Hickman called the body condition score for mouse research “the most valuable tool in the humane endpoints tool chest.” It can also be used for other animals, including rats, rabbits, companion animals and macaques.
When zebra fish are involved, “there is an extensive body of literature regarding behavioral characteristics of zebrafish that can assist in the development of deviations from the zebrafish ethogram,” said Hickman. For example, “changes in swim pattern associated with a predator threat” can be examined, and “tracking software to assess behavioral interactions between fish” may also be used.
Additionally, the “grimace score” may be considered, Hickman said.
“This is one of those objective assessment tools that has been primarily described for determining whether analgesics are operating in the way they are expected to,” Hickman said. “But when you are looking at end of life in an ill animal, the grimace scale will also give you information about whether the animal is experiencing pain or distress. One of the caveats, though, is that there is this effect of cage-side analgesia where when you are staring at the animal to try and determine what its grimace scale score is, you could inadvertently make the animal not express those behaviors.”
Death a Humane Endpoint?
Using death as a humane endpoint is a “difficult” issue, Hickman said. In such research models, an animal “cannot be euthanized prior to death,” such as in an infectious disease study examining toxicity: “where you’re looking at toxicity, if you intervene and euthanize the animal before death, you may end up skewing results.”
Hickman said that, at her institution, “we ask a lot of questions of scientists who’d like [to specify] death as an endpoint in studies.”
When death by euthanasia is a humane endpoint in a study, IU’s IACUC “tends to like having our scientists partner with our veterinarians to assess the monitoring [to] see whether more frequent monitoring [is necessary] or identify a parameter that can help us do that euthanasia early. And I think that falls from my philosophy as the attending vet that these should be rare, that as much as possible we should try to ensure that we are euthanizing prior to the animal suffering and then dying without that alleviation of that pain and suffering,” said Hickman.
Related to this, Hickman addressed whether a certain percentage of weight loss could trigger a humane endpoint; she said this varies among studies.
For instance, “a growing animal should always be growing, so if its body weight is staying stable, that’s a problem. And tumor studies [also have] inherent problems [of] the bulk of the tumor versus muscle loss,” she said.
“In general, I think most of us are pretty comfortable saying that a loss of 20% body weight from baseline, or 20-to-25ish, could be considered an indicator that it might be time to euthanize the animal,” Hickman said.
She emphasized, however, that “I’m a much bigger fan of [using] body condition score, because I think it gives you more information than just weight.”
Citing Weight Loss Prompts Questions
At IU, “if you just write weight loss, I’ll ask you how frequently you’re weighing the animals and what interval, and how you’re comparing to baseline,” Hickman said, because these details are important.
One strategy is to specify appropriate humane endpoints that correlate to particular procedures that might be part of any study, plus to the study generally.
Hickman said this is a practice at some institutions and may help ease administrative effort to develop endpoints “because then the investigator doesn’t have to come up with that list every time.” This could be appropriate, for example, when most of the animals are used for breeding or don’t undergo procedures that trigger a “significant need” for customized endpoints.
IACUC members and veterinary staff could articulate, in advance, “when we see these things, it’s time for the animal to be euthanized,” Hickman said. “What that does is covers the vast majority of the cases at the institution. But you need to make sure that you leave that approach flexible enough so that, for the scientist who needs to have different endpoints…it’s customizable for them,” Hickman said. She warned “not to fall in the trap of just [using criteria of] hunched posture, dehydrated, weight loss.”
OLAW will hold its final webinar of 2018 on Dec. 13. The topic will be the required semi-annual review, featuring speakers from the University of Michigan: Dawn O’Connor, director of the Animal Care & Use Office, and Bill Greer, assistant vice president for research.
Link to webinar transcript:http://bit.ly/2RT2bFI
Link to webinar video: http://bit.ly/2ymFPo5
Link to webinar slides:http://bit.ly/2EFEtdN