Although at the beginning of 2000 some interest was focused on chronic pain and its effect on the quality of life of pets, recent years have been crucial to increase awareness not only in veterinary practitioners, but also in owners.
Adrian et al (2017) suggested adaptive and maladaptive pain, instead of acute and chronic, as better terminology for these concepts when time results in a factor that complicates understanding of the pathophysiology of pain.
Maladaptive pain refers to a chronic condition in which pain does not function as a protective mechanism and is primarily due to plastic alteration in the processing system of pain. Both neuropathic and functional pain are a subclassification of this pain.
Neuropathic pain is due to central or peripheral neural tissue damage; meanwhile, alterations of the nociceptive system with no associated inflammation or neural lesions defines functional pain.
A study by Enomoto et al (2020), during development of a checklist for the detection of degenerative joint disease-associated (DJD) pain in cats, remarked the fact that pets with long-term pain conditions produce gradual behavioural changes that are barely noticed by the owners or associated to ageing.
Therefore, the use of available tools in veterinary medicine will help to create simple, practical and clear communication with owners of pets suffering from maladaptive pain, which is mandatory and important to improve outcome and quality of life for them.
Home videos
Although home videos are not a validated tool, to the author’s knowledge and experience, media information (videos) offers subjective information with a certain degree of feasibility when combined with validated and reliable instruments.
It is recommended to clearly communicate to the owner to follow the same video recording pattern (time of the day, length, location), which allows both the owner and clinician to have certain uniformity. Written instructions (via paper or digital media) about proper recommendations will help the practitioner to collect valuable data to assess together with other tools.
Gait analysis
Although promising results have been shown with gait analysis in dogs with osteoarthritis (OA), one study debates the use of this test to assess chronic pain in dogs with OA compared to healthy dogs (Nielsen et al, 2020).
Gait analysis was performed in 41 healthy dogs and 21 dogs with OA to assess the results per group, and to compare between them. Although the analysis revealed high precision to calculate ground forces in healthy dogs, the authors found a large overlap in ground forces values between both groups. Therefore, abnormal gait analysis in OA dogs is not recommended to be performed by gait analysis mattress.
Addison and Clement (2017) found that kinetic gait analysis is a repeatable technique in non-acclimatised cats, but it is a very time-consuming test. Although some reinforcement was performed, this could be helpful in some cases, but delaying in most of them. Therefore, gait analysis is a challenging test with limited clinical utility in cats with OA.
Actigraphy
Early articles have shown that accelerometer-based motor activity monitoring generates objective data to use during chronic pain assessment in cats.
Some authors have shown that OA cats have low levels of activity during night-time compared to healthy cats; therefore, the evaluation is recommended to be focused on that period of time.
Accelerometer-based motor activity has been assessed using a collar-attached sensor in a population of 42 cats with an abnormal orthopaedic examination, either with or without radiographic OA. This population of cats received a daily oral dose of meloxicam (0.025mg/kg to 0.05mg/kg) during a four-week period, which showed a dose-dependent increase in the activity during night-time (3.7% to 5.2%) compared to the placebo period.
However, in a more recent study, different authors suggested the morning and evening peak on the weekdays are better periods to assess changes in OA cats with an analgesic plan, because it was when the activity of cats with DJD showed lower levels of activity compared to healthy cats; therefore, the possibility to increase their interaction with owners.
Clinical metrology instruments for dogs
Canine brief pain inventory
Canine brief pain inventory (CBPI) is an easy questionnaire with psychometric properties. By the end of the decade of 2000, Brown et al (2009) demonstrated the validation, reliability and responsiveness of this instrument to use in dogs with chronic pain.
A study was performed in 70 dogs with OA, in which CBPI was used to assess the effectiveness of treatment (carprofen 4.4mg/kg by mouth) compared to a placebo during a two-week period. Measurement of CBPI in both groups was performed at day zero (when either placebo or treatment was initiated), and at day 14. Meanwhile, the placebo group showed no significant differences in pain severity and interference scoring, while dogs receiving carprofen showed a significant reduction in both scoring values. Therefore, the authors recommended the use of the CBPI to obtain quantifiable assessments from owners regarding the severity and impact of chronic pain, and treatment for dogs with OA.
Furthermore, the same authors studied CBPI in 100 dogs with a bone cancer diagnosis. Once the owners completed the CBPI, results showed a reliability of this instrument to assess owners’ perspectives of the severity on chronic pain in their dogs with bone cancer.
Helsinki chronic pain index
The Helsinki chronic pain index (HCPI) is a Finnish index developed at the University of Helsinki, in which 11 questions or items are used as a survey for the owners of dogs that suffer from chronic pain.
Hielm-Bjorkman et al (2009) collected questions for topics related to the clinical experience of the authors, previous research, literature, and informal interviews with owners and colleagues. Further revision of the questions headed to a refined questionnaire with 25 items, but 14 of them were removed (due to being not applicable to all owners, not easily understood or not revealing a significant difference between healthy and diseased dogs).
Finally, the 11-item instrument was tested for its validity, reliability and sensitivity after recruiting 34 owners of dogs with signs of chronic pain related to OA.
During a 16-week period, dogs were divided in two groups (placebo and treatment group, with carprofen 2mg/kg twice daily). HCPI was filled by owners at the beginning of the study (week zero), and two, four, eight, 12 and 16 weeks later. Results of the study showed the Finnish version of the HCPI is an easy-to-use, reliable and valid single instrument for evaluation of chronic pain in dogs with signs of OA.
Liverpool osteoarthritis in dogs
Liverpool osteoarthritis in dogs (LOAD) is a clinical metrology instrument (CMI) developed at the University of Liverpool, initially being validated to assess elbow OA in the Labrador retriever, with a total number of 31 items (LOAD-e).
After 24 owners showed problems with answering some of the questions, the research group refined the questionnaire to 14 items.
Although this former LOAD-e showed validity, questions raised related to responsiveness and owner-derived information. However, Walton et al (2013) demonstrated criterion validity for LOAD and CBPI in a cohort study with 222 dogs with OA, in which force-plate analysis was performed together with the evaluation of the previously mentioned CMIs (CBPI; HCPI).
Sleep and night time restlessness evaluation
Sleep-time disturbances and increased restlessness are related to chronic pain due to OA. Sleep and night time restlessness evaluation (SNoRE) is a six-item owner questionnaire with no previous validation, and with the aim to assess quality of sleep of dogs over a one-week period. It was developed at the Comparative Pain Research Laboratory of the College of Veterinary Medicine at North Carolina State University and based on observations of painful dog behaviors.
In a blinded, placebo-controlled crossover study (2015), conducted over a five-week period, 19 dogs with impaired mobility were randomly given either placebo or meloxicam (0.2mg/kg orally, followed by 0.1mg/kg orally once per day) during two weeks, followed by a one-week wash-out period, followed by another two weeks of either meloxicam or placebo.
SNoRE scoring needed to be completed by the owner at days 14, 21, 28 and 35. Although displaying subjective values, treatment with meloxicam showed benefits during sleep and night time based on SNoRE scoring.
Health-related quality of life assessment in dogs
Wiseman-Orr et al (2004) elaborated a questionnaire to measure the effects of chronic pain on health-related quality-of-life assessment (HRQL) in dogs. The study, conducted at the University of Glasgow Small Animal Hospital, started with the compilation of data to conform the different domains related to behavioural changes, including information collected based on audiotapes and interviews to 17 owners with dogs with a chronic condition causing pain.
For the following phase of the study, two types (positive and negative) of descriptor-generating questionnaires were available for owners during a two-month period of time, being completed by a total of 165 owners.
Information from both phases helped the authors to conform a preliminary questionnaire, which was reviewed by 10 owners and 12 clinicians. The final HRQL-structured questionnaire included a large number of items across a few domains, but with an easy design to allow owners to provide detailed information. Some years later, the same group of researchers were able to validate the questionnaire after its use in owners of 26 healthy dogs and 108 dogs with signs of chronic DJD.
CMI for cats
Client-specific outcome measure
At the beginning of the century, the Comparative Pain Research Laboratory of the College of Veterinary Medicine at North Carolina State University adapted a client-specific outcome measure (CSOM) to assess treatment effects in geriatric, arthritic dogs for use in cats.
In essence, the owner describes the problem in motility related to the disease (OA) in the left column and indicates how problematic it is, comparing to when the cat was healthy. During research, the authors found improved scoring of the CSOM compared to baseline when cats were treated with meloxicam (0.1mg/kg by mouth first day, followed by 0.05mg/kg by mouth for the next four days); therefore, it is a subjective tool for owners to detect pain-related behaviours.
A similar questionnaire was used by another research group, called the “Owner Behaviour Watch” (OBW; 2009). As the previous study, it compares the degree and changes regarding general activity, mobility, temperament and grooming, and one question about the overall ability to perform certain tasks (examples were given to the owner) of the cat when it was healthy and/or younger.
Although no placebo group was used, 23 cats were enrolled in the study, in which meloxicam was orally given daily during 28 days. Both owners and veterinary clinicians filled in the questionnaire before and after the treatment, showing good correlation between both of them at day zero.
While some discrepancies were found after 28 days treatment, the OBW helped the owners to realise faster about signs of deterioration of their cats when treatment was not given (four weeks later).
Feline musculoskeletal pain index
Zamprogno et al (2010) recruited 100 client-owned cats with DJD based on radiographs and signs of pain to assess a series of questions related to activity. After interviewing owners, a total of 19 items were identified, of which 12 items showed potential properties to be included in the instrument.
Also, six preliminary designs for instruments were presented to owners, veterinarians and statisticians, a five-point descriptive instrument being the preferable choice for owners and veterinarians.
This study was the original group of questions used to develop the feline musculoskeletal pain index (FMPI) a few years later.
Although, initially, the components of the FMPI showed the ability to distinguish between cats with DJD and healthy cats in a study with 32 client-owned cats, the same research group found that FMPI and actinography scores were not positively correlated, but also, FMPI showed low responsiveness and criterion validity.
However, a later study with 142 cats diagnosed with OA (based on history, orthopaedic examination, and radiographs) revealed the FMPI is the CMI with the most extensive reliability and validity, and the authors recommend it for daily clinical use.
Feline musculoskeletal pain screening checklist
In essence, the feline musculoskeletal pain screening checklist (feline MiPSC) is a proposed checklist not only to help vets during screening cats with DJD, but also to make owners aware about pain signs related to DJD in their cats.
After collecting data of a total of 302 cats (249 with DJD and 53 normal cats) from five studies, nine initial questions were identified to be included in the feline MiPSC.
However, after a removal-questions phase, a total of five binary questions finally completed the questionnaire, due to their levels of sensitivity and specificity for cats with DJD.
HRQL
Cat health and well-being
Freeman et al (2016) studied the relationship between owners and cats to identify the factors that were important and related to HRQL.
Once these factors were determined, the authors collected all data to develop a reliable and valid questionnaire: cat health and wellbeing (CHEW). An initial qualitative phase with 54 client-owned cats determined 11 domains in 100 items.
The second quantitative validation phase was performed with a number of 1,303 cats, which were divided in two groups: the development (information for final instrument) and the validation dataset (to confirm reliability and validation).
Finally, a refined instrument with a total of 33 items in eight domains showed good results about validity, and also internal test-retest reliability.
Feline quality-of-life questionnaire
The feline quality-of-life (QOL) measure is a questionnaire with a total of 16 items. After 45 cat owners completed a survey about which behaviours would indicate a healthy life in their pets, a draft instrument with 23 items was designed.
The qualitative phase of this initial instrument with 10 owners resulted in a 22-item questionnaire. Validation and reliability of this last instrument was performed by psychometric evaluation in 199 owners, and completing the questionnaire twice. Finally, a 16-item instrument showed a strong reliability and validity in healthy cats.
VetMetrica HRQL for cats
VetMetrica is a structured questionnaire instrument completed via online survey, which contains 20 behaviour-related items in three domains (vitality, comfort and emotional well-being). Recently, its validation, responsiveness and agreement between both owners and veterinarians have been studied in a population of 140 cats with a diagnosis of OA (Scott et al, 2021).
Results corroborated the validity of this instrument and its usefulness as a tool to validate the efficacy of treatments for OA cats.
Also, the study showed the good correlation between owners and veterinarians about the effect of the OA disease in the daily life of cats.
- References available on request.
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