A systematic review on the measurement properties of pain scoring instruments in farm animals

This systematic review aimed to investigate evidence on measurement properties of pain scoring instrumentsin farm animals.A registered report protocol was published with the methodology (Tomacheuski et al. 2021). Studies reporting the development and validation of acute and chronic pain scoring instruments based on behaviouraland/or facial expressions of farm animals (bovine, ovine, caprine, camel, swine and poultry) were included.Data extraction and assessment were performed individually by two investigators using the Consensus‐basedStandards for the Selection of Health Measurement Instruments (COSMIN) guidelines (Prinsen et al. 2018).Nine categories were assessed: general design requirements and scale development, content validity andcomprehensibility, internal consistency, reliability, measurement error, criterion and construct validity, responsiveness, and cross-cultural validity. Overall strength of evidence (high, moderate, low, or very low) ofeach instrument was scored based on methodological quality, number of studies and studies’ findings. 

Twenty instruments for three species (bovine, ovine and swine) were included. Three behavior-based instruments scored overall high evidence: UCAPS (Unesp-Botucatu Unidimensional Composite Pain Scale for assessing postoperative pain in cattle), USAPS (Unesp-Botucatu Sheep Acute Composite Pain Scale) and UPAPS(Unesp-Botucatu Pig Composite Acute Pain Scale). Four instruments scored overall moderate evidence: MPSS(Multidimensional Pain Scoring System for bovine), SPFES (Sheep Pain Facial Expression Scale), LGS (LambGrimace Scale) and PGS-B (Piglet Grimace Scale-B). Most instruments scored overall low or very low strengthof evidence. 

Pain scoring instruments showed considerable variability regarding their measurement properties. Instruments with reported validation are urgently required for pain assessment of goat, camel and avian species.