Inter-rater and inter-device reliability of mechanical thresholds measurement with the Electronic von Frey Anaesthesiometer and the SMALGO in healthy cats

Pressure pain mapping of equine distal joints: feasibility and reliability

Background

Osteoarthritis is a prevalent degenerative joint disease initiating chronic pain and lameness in horses. While several objective gait analysis systems have been developed and validated to quantify lameness severity in horses, methods to evaluate whether peripheral sensitization contributes to the pain experienced are missing.

Objectives

To evaluate whether periarticular pressure pain mapping could be proposed as an auxiliary assessment tool in horses. Specific aims were to evaluate the feasibility and intra- and inter-rater reliability of pressure pain thresholds (PPT) determination at sites overlying the distal thoracic limb joints of clinically healthy horses.

Study design

Prospective, randomized validation study.

Methods

For feasibility assessment, PPT were measured with a hand-held digital algometer at six periarticular landmarks (2 sites per joint, 3 joints) bilaterally on the distal thoracic limb of 40 healthy horses (20 warmblood and 20 Freiberger). The joints tested were the metacarpophalangeal, on the latero-palmar and dorsal aspects (L-MCP and D-MCP), the proximal interphalangeal, on the dorsal and palmar aspect (D-PIP and P-PIP) and the distal interphalangeal, on the dorsal and lateral aspect (D-DIP and L-DIP). A feasibility score, ranging from 0 to 5, was attributed to each testing session. For intra- and inter-rater reliability assessment, L-MCP and D-MCP were selected to be tested again at 2 weeks intervals in 20 out of the 40 horses. Data were analyzed using a mixed-effect linear model to test differences in threshold per site and limb. Intra- and inter-rater correlation was calculated. Bland-Altman plots were performed to evaluate the variability of the measures.

Results

The procedure was considered feasible (score <2) in 95% of horses (95% CI 88%-100%). Overall, median [interquartile range (IQR)] PPT was 9.4 (7.5-11.3) N. No significant side differences were found. P-PIP and D-DIP recorded significantly lower PPT (p < 0.001 and p = 0.002, respectively) than L-MCP. Median (IQR) were 9.9 (7.3-12.4) N, 8.4 (6.1-10.5) N and 9.0 (7.4-10.6) N for L-MCP, P-PIP and D-DIP, respectively. The intra-rater agreement was 0.68 (95% CI 0.35-0.86) for L-MCP, and 0.50 (95% CI 0.08-0.76) for D-MCP. Inter-rater agreement was 0.85 (95% CI 0.66-0.94) for L-MCP and 0.81 (0.57, 0.92) for D-MCP.

Main limitations

Evaluation of feasibility was performed only for distal thoracic limbs joints; no data are provided for hind limbs or proximal joints. Only warmblood and Freiberger horses were included. Intra- and inter-rater reliability assessments were performed exclusively on data collected at the MCP joint.

Conclusion

Pressure pain mapping of distal thoracic limb joints was feasible in horses. Local sensitivity differed among sites and no side differences were noticed. Data collected from the MCP joint suggest highly variable, subject dependent intra-rater reliability, ranging from poor to good, and good to excellent inter-rater reliability. Further studies evaluating pathologic vs. healthy joints are needed before recommendations can be made about clinical usability and diagnostic validity.

Evaluation of the analgesic efficacy of grapiprant compared with robenacoxib in cats undergoing elective ovariohysterectomy in a prospective, randomized, masked, non-inferiority clinical trial

OBJECTIVES

The main objective of this study was to compare the postoperative analgesic effects of grapiprant with those of robenacoxib in cats undergoing ovariohysterectomy (OVH).

METHODS

In total, 37 female cats (age range 4 months-10 years, weighing ⩾2.5 kg) were enrolled in a prospective, randomized, masked, non-inferiority (NI) clinical trial. Cats received oral robenacoxib (1 mg/kg) or grapiprant (2 mg/kg) 2 h before OVH. Analgesia was assessed via the Feline Grimace Scale (FGS), the Glasgow Composite Measure Pain Scale-Feline (CMPS-F), von Frey monofilaments (vFFs) and pressure algometry (ALG) 2 h before treatment administration, at extubation, and 2, 4, 6, 8, 18 and 24 hours after extubation. Hydromorphone (<8 h postoperatively) or buprenorphine (>18 h postoperatively) were administered to cats with scores of ⩾5/20 on CMPS-F and/or ⩾4/10 on FGS. NI margins for CMPS-F and vFFs were set at 3 and -0.2, respectively. A mixed-effect ANOVA was used for FGS scores (P <0.05). Data are reported as mean ± SEM.

RESULTS

The data from 33 cats were analyzed. The upper limit of the 95% confidence interval (CI) (0.35) was less than the NI margin of 3 for CMPS-F, and the lower limit of the 95% CI (0.055) was greater than the NI margin of -0.2 for vFFs, indicating NI of grapiprant. The FGS scores were greater than baseline at extubation for both treatments (1.65 ± 0.63; P = 0.001); however, there was no difference between treatments. There was no difference between treatments, nor treatment by time interaction, for vFFs (P <0.001). The CMPS-F scores for both treatments were higher at extubation but returned to baseline after 4 h (P <0.001). For ALG, there was no difference in treatment or treatment by time interaction. The robenacoxib group had lower pressure readings at extubation and 6 h compared with baseline.

CONCLUSIONS AND RELEVANCE

These results indicate that grapiprant was non-inferior to robenacoxib for mitigating postsurgical pain in cats after OVH performed via ventral celiotomy. The impact of grapiprant for analgesia in OVH via the flank is unknown.

Use of mechanical thresholds in a model of feline clinical acute pain and their correlation with the Glasgow Feline Composite Measure Pain Scale scores

OBJECTIVES

The aim of this study was to evaluate the use of mechanical thresholds (MT), measured with the SMALGO (Small Animal ALGOmeter), and to determine whether there was a correlation between MT and Glasgow Feline Composite Measure Pain Scale (CMPS-Feline) scores in cats undergoing ovariohysterectomy.

METHODS

Client-owned cats undergoing flank ovariohysterectomy were recruited. Pain scores for the pre- and postoperative periods were obtained using the CMPS-Feline in each cat by two independent investigators (A and B). Following CMPS-Feline scoring, MT were measured with the SMALGO, in the surgical area, pre- and postoperatively, only by investigator A. Each cat served as its own control for the comparison of pre- and postoperative variables. Reliability statistics were used to assess the level of inter-observer agreement (A vs B) with respect to pre- and postoperative CMPS-Feline scores, while Spearman's correlation statistics were used to analyse the relationship between MT and CMPS-Feline scores.

RESULTS

Twenty-nine cats completed the study. Preoperative MT (340 g [range 108-691]) were significantly higher than postoperatively (233 g [range 19-549]; P = 0.001). CMPS-Feline scores were not found to differ significantly between the preoperative period (2 [range 0-7] for investigator A and 3.2 ± 2.3 for investigator B) and postoperative period (2 [range 0-10] for investigator A and 3 [range 0-8] for investigator B) for either investigator. Reliability statistics revealed that the level of inter-observer agreement with respect to CMPS-Feline was fair for the preoperative assessments but poor for the postoperative evaluations. There was no correlation between MT and CMPS-Feline scores.

CONCLUSIONS AND RELEVANCE

Although there was no correlation with CMPS-Feline scores performed at the same timepoint, MT increased postoperatively vs baseline. Assuming that, despite analgesia, susceptibility of the surgical area to mechanical stimulation would increase after surgery, this finding suggests that MT might be useful to assess feline surgical pain. The poor level of inter-observer agreement with respect to postoperative CMPS-Feline scores highlights the potential limitations of this scale.

Serum artemin is not correlated with sensitivity within dogs with naturally occurring osteoarthritis pain

Osteoarthritis (OA) pain is associated with peripheral and central sensitization in humans and results in widespread increased sensitivity across the body. Sensitization contributes to the OA-associated pain (OAP) state. We recently identified increased levels of an endogenous neurotrophic factor, artemin (ARTN), in dogs with OAP compared to healthy pain-free controls. Circulating ARTN released from damaged tissues in OA, may play a central role in widespread sensitivity and pain. However, the relationship between ARTN and somatosensory sensitivity remains unknown. The study aimed to assess the relationship between serum ARTN concentrations and measures of sensitivity in dogs with OAP using quantitative sensory testing. We hypothesized that there would be a positive association between circulating ARTN and increased sensitivity to mechanical and thermal stimuli in dogs with OAP. We used linear and logistic regression models to assess the relationship between ARTN, sensitization, and pain within a cohort of 43 dogs with spontaneous OAP. Serum ARTN was not associated with the degree of sensitization within dogs with OAP. Further, across dogs with varying OAP severity, we did not find any association between ARTN, and clinical measures of joint pain and disability. Although a relationship between ARTN and joint pain was not ruled out.

Inter- and intra-observer reliability of quantitative sensory testing performed with the SMall animal ALGOmeter (SMALGO) to evaluate pain associated with feline gingivostomatitis

OBJECTIVES

The aim of this study was to evaluate the inter- and intra-observer reliability of quantitative sensory testing performed with the SMall animal ALGOmeter (SMALGO) in healthy cats and in cats with chronic gingivostomatitis (CGS), and to evaluate the SMALGO as a tool to detect and quantify pain in cats with CGS.

METHODS

Thirty cats from a private shelter were included and assigned to one of two groups: group C (healthy cats; n = 15) or group CGS (cats with CGS; n = 15). In all cats the mechanical thresholds were measured with the SMALGO, with the sensor tip applied to the superior lip above the canine root, by two independent investigators (A, experienced; B, unexperienced), on two different occasions (day 1 and day 2) with a 24 h interval. A CGS scale was used in the diseased cats to assess the severity of the condition. For the reliability analysis, intra-class correlation coefficients (ICCs) were calculated. Other statistical tests used were Pearson correlation coefficient and a paired t-test.

RESULTS

The inter- and intra-observer levels of agreement were fair (ICC = 0.50) and good, respectively (ICC = 0.73 for investigator A; ICC = 0.60 for investigator B). However, the thresholds measured in healthy cats (169 ± 59 g) did not differ from those obtained from diseased cats (156 ± 82 g; P = 0.35). There was no correlation between the scores of the CGS scale and the thresholds measured in diseased cats (Pearson correlation coefficient = 0.047; P = 0.87).

CONCLUSIONS AND RELEVANCE

Quantitative sensory testing performed with the SMALGO in cats is repeatable and reliable, regardless of the expertise of the investigator. However, the findings of this study suggest that the mechanical thresholds measured with the SMALGO may not be a valuable indicator of pain in cats with CGS.

Use of nociceptive threshold testing in cats in experimental and clinical settings: a qualitative review

OBJECTIVE

The objective of this study was to review the scientific articles on the use of nociceptive threshold testing (NTT) in cats and to summarize the clinical and experimental applications in this species.

DATABASES USED

Pertinent literature was searched with PubMed, Scopus, Web of Science, Universitätsbibliothek Basel (swissbib Basel Bern) and Google Scholar. The search was then refined manually based first on article titles and abstracts, and subsequently on full texts.

CONCLUSIONS

Of the four classical acute nociceptive models used for NTT, thermal and mechanical are most commonly used in cats. Thermal stimulation is applicable in experimental settings and has been used in pharmacodynamics studies assessing feline antinociception. Although mechanical stimulation is currently less used in cats, in the future it might play a role in the evaluation of clinical feline pain. However, the low response reliability after stimulus repetition within a narrow time interval represents a major limitation for the clinical use of mechanical thresholds in this species. Challenges remain when thermal thresholds are used to investigate analgesics that have the potential to affect skin temperature, such as opioids and α2-adrenergic agonists, and when a model of inflammatory pain is reproduced in experimental cats with the purpose of evaluating non-steroidal anti-inflammatory drugs as analgesics.