Most clinical problems and a significant number of scientific studies involve pain. Pain identification, followed by attitudes towards proper analgesia are imperative to guarantee animal welfare.
Although oligoanalgesia is still a reality, it is notorious that antalgic therapy has evolved qualitatively and quantitatively in the last three decades, possibly credited to a better understanding of physiopathology and the development of pain assessment methods. Indeed, pain assessment is the cornerstone for deciding whether to provide analgesia and select the most appropriate antalgic therapy in the clinical and research setting.
Objective and subjective methods may be employed to assess pain. Objective methods, like physiological data, nociceptive tests, and locomotor activity are less affected by the observer´s judgment, however they are overall non-specific, may be intrusive/invasive, costly when demanding equipment, and in case of laboratory tests, may consume time and results are not promptly available. Otherwise, pain-related behaviour assessment is a subjective non-invasive method, that does not require equipment and may be performed remotely in the clinical and research scenario.
A behaviour-based pain scale should not only be short, easy, and fast filling. It must be reliable and valid before being applicable in clinical practice or research. Validity guarantees that the instrument measures what has been planned and reliability ensures repeatability and reproducibility. Other important properties of a pain assessment instrument are item interrelation, mutual association, and homogeneity. Finally, the cherry on the cake is defining a cut-off score to orient decision-making for analgesic intervention. Unidimensional scales (visual analogue, simple descriptive, and numerical scales) do not retain these properties. Although they may be simpler and faster when compared to composite scales, they have limited reproducibility and do not encompass the complexity of pain.
The COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN, https://doi.org/10.1016/j.jclinepi.2010.02.006) and GRADE (Grading of Recommendations, Assessment, Development, and Evaluations, https://doi.org/10.1136/bmj.39489.470347.AD), are well-recognized methods to support the quality of evidence and strength for the recommendation of a given instrument (World Health Organization). Until 2011 there were only two pioneer instruments with some level of evidence to assess pain in dogs (The University of Melbourne Pain Scale in 1999, and The Glasgow Composite Measure Pain Scale in 2001 & 2007, and the Composite Orthopaedic Pain Scale in horses. These instruments opened the doors for creating scales in other species.
Because cats still received less analgesia than dogs by that time, our group was motivated to develop accurate instruments to facilitate pain assessment and encourage antalgic therapy in other animals. In chronological order, the following behaviour composite scales have been submitted to psychometric tests and published in cats:
The Unesp-Botucatu Feline Pain Scale (UFEPS) 2011 & 2013
The Glasgow Feline Composite Measure Pain Scale (CMPS-Feline 2014 & 2017
The Feline Grimace Scale 2019
They may all be used to assess clinical, soft tissue, or orthopaedic postoperative pain, and in the case of UFEPS, oral cancer pain as well. According to the World Small Animal Veterinary Association (https://doi.org/10.1111/jsap.13566) they have moderate (CMPS-Feline) and high levels of evidence (UFEPS, UFEPS-SF and FGS).
By following the COSMIN criteria our group developed and validated the following acute pain scales in other animal species: cattle (2014, https://doi.org/10.1186/s12917-014-0200-0), horses (2015, https://doi.org/10.1186/s12917-015-0395-8 and 2021, https://doi.org/10.1371/journal.pone.0255618), sheep (2020; https://doi.org/10.1371/journal.pone.0239622), pigs (2020; https://doi.org/10.1371/journal.pone.0233552), , donkeys (2021; https://doi.org/10.3389/fvets.2021.671330), rabbits (2022; https://doi.org/10.1371/journal.pone.0268973), piglets (2023 https://doi.org/10.1371/journal.pone.0284218), goats (2023, https://doi.org/10.3390/ani13132136), as well as the Portuguese version of canine brief pain inventory (2022; https://doi.org/10.1590/1678-4162-12542) with a defined cut-off point.
After validating these instruments, the next natural step was to popularize and facilitate their use beyond the academic and scientific world. To that, our group developed the website www.animalpain.org and the free Vetpain application (Tutorial video: https://youtu.be/ahZIB0QhJjk). It is possible to download the application worldwide for Android (https://play.google.com/store/apps/details?id=com.vetpain.app) and IOS (https://apps.apple.com/ca/app/vetpain/id6462712970). Vetpain may be used to assess acute pain in all laboratory and domestic mammals, and, for some species, sedation, and chronic pain.
Why should veterinarians incorporate this into their practice? By using Vetpain, veterinarians, students, nurses, or animal caretakers/owners may assess videos demonstrating the behaviours corresponding to all pain scale items, to improve their learning, accuracy, and reliability. There are videos for training and teaching, where the users can check their knowledge according to the template, before using the scales on their animals, as well as it can be useful for teaching purposes. Users can evaluate pain in clinical or research animals with automatic calculation of scores. Data may be shared among the staff, and because the data are stored, previous pain assessments can be compared to current ones, to follow the efficacy and duration of antalgic therapy. The indicative cut-off scores offer assertive information to orient the clinician's decision to provide analgesia for animals suffering pain, minimizing the risk of oligoanalgesia.
Vetpain: the app developed to measure pain in animals.
Vetpain includes validated scales that assess sedation and acute and chronic pain in all domestic species.
Species | Acute Pain | Chronic Pain | Sedation |
Cat | · Unesp-Botucatu Feline Pain Scale (Brondani et al 2013) · Short form if the Unesp-Botucatu Feline Pain Scale (Luna et al 2022) | · Signs of osteoarthritis |
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Dog | · Short-Form Glasgow Composite Measure Pain Scale (Reid et al 2007). · University of Melbourne Pain Scale (Firth & Haldane 1999). · 4A-Vet (Rialland et al 2012) | · Canine Brief Pain Inventory (CBPI) (Brown et al. 2008, 2009) · Liverpool Osteoarthritis in Dogs (LOAD) (Walton et al. 2013) · Canine OA Staging Tool (COAST) (Cachon et al 2023) · Quality-of-life for cancer pain (Yazbek & Fantoni 2005) | · Abbreviated sedation scale (Wagner et al 2017) |
Rabbit | · Rabbit Pain Behaviour Scale (Haddad Pinho 2022) |
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Mice | · Mouse Grimace (Langford et al 2010) |
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Rat | · Rat Grimace (Oliver et al 2014) |
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Guest post written by;
Senior Professor Stelio Pacca Loureiro Luna, DVM, Msci, PhD, Diplomate ECVAA, IVAS cert
Department of Veterinary Surgery and Animal Reproduction
School of Veterinary Medicine and Animal Science (FMVZ)
University of São Paulo State (Unesp)
Botucatu – São Paulo – Brazil
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