Abstract
OBJECTIVE
To assess the repeatability of infrared thermometer temperature readings and evaluate the correlation between digital rectal temperature and infrared thermometer temperatures taken at different locations in healthy afebrile horses.
ANIMALS
101 afebrile horses ≥ 1 year old.
METHODS
Digital rectal temperatures and infrared temperatures from the eye, gingiva, neck, axilla, and perineum were obtained in a climate-controlled environment and at 2 outdoor ambient temperatures (study period, November 1, 2021, to April 30, 2023).
RESULTS
Infrared temperature measurements were well tolerated by horses, including those resistant to rectal temperature. There was significant correlation between rectal temperature and infrared temperature taken at the perineum (R = 0.57; P < .001) and eye (R = 0.37; P < .001). Infrared temperature measurements were highly repeatable, allowing for calculation of reference ranges for the perineum (36.0 to 37.8 °C) and eye (35.7 to 37.1 °C) in climate-controlled conditions. There was increased variance in outside temperatures compared to climate-controlled conditions for the eye (P = .002), gingiva (P = .047), and perineum (P = .005).
CLINICAL RELEVANCE
While infrared thermometer temperatures were not numerically the same as rectal temperature using a digital thermometer, measurements at the perineum and eye were correlated with rectal temperature readings. Further, the repeatability of infrared readings allows for computation of reference ranges that make the infrared thermometer a viable alternative for the practicing veterinarian when obtaining a temperature in uncooperative horses. The infrared thermometer was reliable outdoors for the eye, but not the perineum. Additional validation of infrared temperature reference ranges in febrile horses and warmer ambient temperatures is warranted.
Introduction
Body temperature of the horse is routinely assessed by measurement of rectal temperature during physical examination. The normal reference range of rectal temperature in horses has been well established and is 37.5 to 38.3 °C.1 While horses are typically tolerant of rectal temperature measurement, young, unhandled, nervous, or ill-tempered horses may strongly object. Horses can cause serious injuries by kicking with 1 hind limb or both hind limbs, presenting an inherent risk to the person measuring the temperature of any horse. The occupational injury risk to equine practitioners is substantiated by a recent survey2; of 620 respondents, 495 practitioners stated that they had sustained at least 1 injury while working with horses. The cause of injury was captured by 493 responses, 242 (49.1%) of which were injury due to hind limb kicks. The high percentage of injuries due to hind limbs warrants concern for the health of the equine practitioner, and measures should be taken to decrease the risk of injury whenever possible.
The gold standard to assess core body temperature involves invasive contact devices, such as esophageal and pulmonary thermistors.3,4 Digital thermometers are a more widely used clinical method for measurement of body temperature in humans (typically used under the tongue) and in veterinary medicine (used rectally), as they do not require invasive procedures for appropriate placement. However, digital thermometers may take up to 60 seconds to report a temperature reading, exposing equine practitioners to the risk of kick injury for a significant period of time. Noncontact infrared thermometers became common for measurement of human body temperature during the COVID-19 pandemic and may be a reasonable option in situations where obtaining a rectal temperature is deemed to be unsafe. However, the accuracy of these thermometers in comparison to digital (contact) thermometers for use in human clinical settings has been questioned. One study4 in children found that the repeatability of a noncontact infrared thermometer was similar to the mercury thermometer, and there was good agreement of measured body temperature. However, in another study testing 6 different infrared forehead thermometers in 1,022 human subjects, 48% to 88% of the individual temperature measurements were outside of the labeled accuracy (± 0.3 °C5) provided by the manufacturers. The infrared thermometers used in that study differed from the oral reference thermometer readings by–3 to +2 °C, rendering the infrared thermometer clinically ineffective.6
Few studies have explored the correlation of infrared thermometer temperature to rectal temperatures in veterinary species. A comparison7 between rectal temperature and infrared thermometer temperature of the cornea in 300 dogs found poor agreement between the 2 measurements. Similarly, a study8 comparing infrared thermometer temperature measurement at the mucogingival junction to a digital rectal thermometer in 40 horses found that the temperature readings were not well correlated, suggesting that infrared thermometer measurement at the mucogingival junction was not an accurate reflection of rectal temperature. A recent study9 compared infrared forehead and neck temperatures to digital rectal temperatures in 142 horses and 34 foals and found that the infrared thermometer reliability was good but that the infrared temperatures were biased by approximately 0.9 °C. However, this study evaluated only areas covered by hair in horses housed outside. The use of alternate hairless locations has not been investigated, nor has repeatability of infrared body temperature measurements been reported under different ambient temperature conditions.
The purpose of this study was to assess the repeatability of infrared thermometer temperature readings and evaluate the correlations between digital rectal temperature and infrared thermometer temperatures measured at different anatomical locations in healthy afebrile horses in climate-controlled conditions. The effect of cold outdoor ambient temperatures on infrared temperature readings was also investigated. We hypothesized that infrared measurements would be highly repeatable, with coefficients of variation (CV) of < 2%, and that at least 1 infrared body temperature measurement would be significantly correlated with the digital rectal temperature measurement. When used to measure the temperature of horses outdoors, we hypothesized that the infrared thermometer measurements would be more variable than when used in climate-controlled conditions. If the hypotheses were supported, the secondary objective of this study was to calculate reference ranges for infrared temperature measurements in healthy horses at specific anatomical locations.
Methods
Study horses
Afebrile horses ≥ 1 year of age presenting to the University of Illinois Veterinary Teaching Hospital between November 1, 2021, and April 30, 2023, were enrolled in a prospective observational study. The study was determined to be exempt from the requirement for institutional approval after consultation with the IACUC, as rectal temperatures were taken during routine clinical evaluation and the comparison procedure was noncontact. Signalment, reason for presentation, weight, body condition score (1 to 9), and hair coat qualities (length and cleanliness) were recorded for each patient.
Climate-controlled data collection
Data collection was performed inside the hospital in a climate-controlled environment, maintained at an average temperature of 22.1 °C. Both thermometers were used as instructed by the manufacturers and reported temperature in degrees Fahrenheit (subsequently converted to Celsius for the purposes of reporting). Digital rectal temperatures for all horses were recorded using the same thermometer (Vicks SpeedRead Digital Thermometer; Kaz USA Inc) 3 consecutive times. For the rectal temperature, the digital thermometer was inserted into the rectum and then started. If the thermometer took > 30 seconds to finalize a temperature reading, the temperature at thermometer timeout was recorded. The thermometer was not removed from the rectum between consecutive readings on the same patient and was disinfected between horses.
Infrared temperatures for all horses were recorded using the same thermometer (Infrared Non-Contact Thermometer; Globe Scientific Inc). The same person operated the infrared thermometer for all horses. Per instructions, the infrared thermometer should be used 5 to 10 cm from the target surface. A cotton swab extending 5 cm past the infrared sensor was secured to the unit to ensure a standardized distance between the horse and thermometer. For each horse, temperatures were recorded at 5 different sites: the gingiva, eye, neck, axilla, and perineum. The temperature was measured 3 consecutive times for each site. To minimize differences in positioning, the left side of the horse was used; if the mane lay on the left neck, the right neck was used. The gingival temperature was taken above the central incisors (101 and 201). To avoid inadvertent injury to the eye, the thermometer was held slightly more distant than the standard 5 cm so the swab did not contact the eye. The neck temperature was taken just cranial and dorsal to the thoracic inlet. The axilla temperature was obtained at the deepest accessible area where the forelimb meets the trunk with the horse standing square in the forelimbs. The perineum was approached from the left side of the horse with the tail lifted and the thermometer directed at midline just below the rectum in males and lateral to the vulva in females.
Outside ambient temperature data collection
Ten university-owned teaching horses were evaluated while housed outdoors at 2 different ambient temperatures at 2 separate time points, 3 weeks apart (January 10 and 31, 2023). Rectal and infrared temperatures (as described earlier in this report) were obtained from the horses at the same time each day so that the ambient temperature was the same for all horses. Rectal and infrared temperatures were also obtained from the same 10 horses indoors under climate-controlled conditions. Horses were indoors for at least 15 minutes before readings were taken.
Statistical analysis
Temperature data were preprocessed in Excel (Microsoft Corp) to convert Fahrenheit to Celsius. Further analysis was performed using standard software (R, version 4.2.1, using RStudio, version 2022.12.0; PBC).10 Normality was assessed via the Shapiro-Wilk test and visual analysis of the data. Normally distributed data are presented as mean ± SD, and nonparametric data are presented as median (quartile 1, quartile 3). Within-subject mean and SD were calculated with standard software (R package matrixStats, version 0.61.0; PBC),11 and the CV was calculated as CV = [SD / mean] X 100. The average of the 3 readings for each site was used for further analysis. Outliers were determined with Horn's method and removed prior to reference range calculation.12 Reference ranges were calculated robustly with 90% CIs calculated by bootstrapping (R package referenceIntervals, version 1.2.0; PBC).13 Effect of age and body weight on the temperature at each site was analyzed by univariate linear regression. Wilcoxon rank sum test was used to assess differences between hair coat variables (clean/dirty and short/long).
The effect of ambient temperature on body temperature was assessed by repeated-measures ANOVA and post hoc pairwise t test with Bonferroni correction for normally distributed data and by Friedman test for nonparametric data, with ambient temperature as the grouping variable and the horse as the blocking variable, and post hoc Wilcoxon rank sum test with Bonferroni correction. The variance in temperature measurements was compared between outdoor and indoor measurements for each body site via the Levene test. Agreement between rectal and infrared temperatures was evaluated by Bland-Altman analysis (R package blandr, version 0.5.3; PBC),14 with 95% CIs. For locations at which infrared temperature measurements were strongly correlated with rectal temperature, a line was fitted by means of the base stats package in R. For all analyses, P < .05 was considered to be significant.
Results
Climate-controlled temperature measurements
There were 101 horses that met the inclusion criteria during the study period. Horse breeds were reflective of the general hospital population and included Standardbred (n = 40), Quarter Horse (27), Thoroughbred (8), Paint Horse (7), mixed breed (4), warmblood breeds (4), Arabian (3), Andalusian (2), Tennessee Walker (2), and draft breeds (2) as well as 1 Appaloosa and 1 Saddlebred. There were 52 mares, 30 geldings, and 19 stallions. Age ranged from 1 to 28 years with a median of 6 years. Hair coat was categorized as long in 37 (36.6%) horses and dirty in 10 (9.9%) horses. Body weight ranged from 341 to 763 kg with a median of 484 kg. Horses presented primarily for arthroscopy (n = 32), lameness examination (15), teaching (14), and colic (10). Other nonelective presentations included fever of unknown origin (3), choke (2), and 1 each of laceration, pleuropneumonia, cystitis, smoke inhalation, cellulitis, and purpura hemorrhagica. All horses were afebrile at the time of data collection. Other elective presentations included wound management (n = 4), companion (3), euthanasia (2), reproductive examination (2), tooth extraction (1), gastroscopy (1), castration (1), sequestrum (1), ophthalmologic examination (1), tie-forward (1), and splint bone removal (1).
Infrared body temperature measurement was subjectively well tolerated by all horses, including those resistant to digital rectal thermometer use. Temperatures were within thermometer range in all horses at the perineum, globe, and gingiva. Neck and axilla temperatures read “Lo” (below the lower limit of the thermometer [32 °C]) in 49 and 47 horses respectively.
Rectal temperature and infrared temperatures were not normally distributed, and nonparametric analyses were performed for all data. Median infrared thermometer temperatures ranged from 34.3 °C at the neck to 37.0 °C at the gingiva (Figure 1; Table 1). Within-subject CV was < 1% for all temperatures and was lowest for the perineal, rectal, and eye temperatures. There was significant linear correlation between rectal temperature and both perineal (R = 0.57; P < .001) and eye (R = 0.37; P < .001) temperatures (Figure 2). Fitted lines were calculated to describe the relationship between temperatures measured at each of these locations and rectal temperatures. Reference intervals with 90% CIs were calculated for rectal, eye, and perineal temperatures (Table 2). Bland-Altman analysis was performed, using the average of the difference in measured temperature, to evaluate bias and agreement between rectal and infrared temperature measurements. Gingiva (0.5 °C [95% CI, 0.43 to 0.47 °C]), eye (1.23 °C [95% CI, 1.17 to 1.29 °C]), and perineum (0.77 °C [95% CI, 0.72 to 0.83 °C]) had the smallest bias relative to rectal temperature (Table 3). Eye and perineum had the narrowest ranges of agreement, at 1.89 and 1.84 °C, respectively.
Digital rectal temperature and infrared temperatures (gingiva, eye, axilla, perineum, neck) of 101 afebrile horses ≥ 1 year of age presenting to the University of Illinois Veterinary Teaching Hospital between November 1, 2021, and April 30, 2023. Temperatures were obtained in climate-controlled conditions (average, 22.1 °C) and are presented as box plots with overlaid violin plots. Box plots indicate the median and quartiles, with whiskers extending to 1.5 times the IQR and dots representing outliers. Violin plots show the density (distribution) of the data. Color corresponds to location of temperature measurement.
Citation: Journal of the American Veterinary Medical Association 262, 6; 10.2460/javma.23.12.0714
Summary statistics for the digital rectal temperature and infrared temperatures (gingiva, eye, axilla, perineum, neck) of 101 afebrile horses ≥ 1 year of age presenting to the University of Illinois Veterinary Teaching Hospital between November 1, 2021, and April 30, 2023. Temperatures were obtained in climate-controlled conditions (average, 22.1 °C) and are presented as median (IQR 1–IQR 3). The within-subject coefficients of variation (CV) at each temperature measurement location are listed.
| Temperature (°C) | CV (%) | |
|---|---|---|
| Rectal | 37.7 (37.3–38) | 0.2 |
| Gingiva | 37.0 (36.9–37.3) | 0.4 |
| Eye | 36.4 (36.1–36.7) | 0.2 |
| Axilla | 34.6 (33.6–35.7) | 0.7 |
| Perineum | 37.0, 36.6–37.2) | 0.2 |
| Neck | 34.3 (33.2–35.7) | 0.4 |
Scatterplots showing linear correlation between rectal and infrared temperatures for each infrared temperature location obtained for 101 afebrile horses, as described in Figure 1. Gray bands represent 95% CIs. R = Pearson's correlation coefficient; P = significance of the correlation. A fitted line was calculated for significant correlations.
Citation: Journal of the American Veterinary Medical Association 262, 6; 10.2460/javma.23.12.0714
Upper and lower reference intervals for rectal and infrared temperatures of horses described in Table 1 in climate-controlled conditions for significantly correlated locations with 90% CIs.
| Reference interval (°C) | 90% lower CI (°C) | 90% upper CI (°C) | |
|---|---|---|---|
| Rectal | 36.7–38.6 | 36.6–36.8 | 38.5–38.7 |
| Eye | 35.7–37.1 | 35.6–35.8 | 37.0–37.2 |
| Perineum | 36.0–37.8 | 35.8–36.1 | 37.7–38 |
Summary statistics for Bland-Altman analysis of bias and agreement for infrared temperatures at the 5 locations relative to rectal temperatures. Graphical results are shown in Supplementary Figure S1. Bias, upper, and lower limits of agreement (LOA) are each presented in degrees Celsius.
| Bias (95% CI) | Lower LOA (95% CI) | Upper LOA (95% CI) | |
|---|---|---|---|
| Gingiva | 0.50 (0.43 to 0.57) | –0.56 (–0.68 to–0.44) | 1.56 (1.44 to 1.68) |
| Eye | 1.23 (1.17 to 1.29) | 0.28 (0.19 to 0.38) | 2.17 (2.08 to 2.27) |
| Axilla | 3.21 (3.00 to 3.42) | 0.79 (0.43 to 1.14) | 5.63 (5.28 to 5.99) |
| Perineum | 0.77 (0.72 to 0.83) | –0.14 (–0.24 to–0.04) | 1.69 (1.59 to 1.78) |
| Neck | 3.37 (3.15 to 3.59) | 0.82 (0.44 to 1.19) | 5.92 (5.55 to 6.29) |
There was no significant difference between temperature measurements for horses categorized as having clean versus dirty hair coats at any location (Supplementary Figure S2). Temperatures measured at the neck were significantly lower (P = .027) in horses categorized as having long hair coats (33.4 °C [range, 32.8 to 33.9 °C]) compared to horses without long hair coats (34.8 °C [range, 33.8 to 35.7 °C]; Supplementary Figure S3). Horse age was inversely related to rectal, eye, and perineal temperatures (P < .001; Supplementary Figure S4).
Outdoor ambient temperature measurements
The 10 horses in this group comprised Quarter Horses (n = 4), Arabians (2), and 1 Missouri Fox Trotter, 1 Tennessee Walker, Thoroughbred, and 1 warmblood. There were 3 geldings and 7 mares that ranged in age from 9 to 25 years with a median of 16.7 years. Hair coat was categorized as dirty in all 10 horses and long in 1 horse. Weight ranged from 409 to 590 kg with a median of 545 kg. The ambient temperatures at the 2 collection time points were 8.9 and–6.7 °C. At 8.9 °C, temperatures were within thermometer range in all horses at the globe and gingiva; perineum, neck, and axilla temperatures read “Lo” in 4, 9, and 10 horses respectively. At–6.7 °C, every horse had at least 1 “Lo” reading. “Lo” readings were obtained at the globe (n = 1), perineum (1), gingiva (1), neck (8) and axilla (10). The “Lo” readings were imputed to the lower limit of the infrared thermometer (32 °C) to facilitate statistical analysis.
Rectal temperature and infrared temperature at the globe were normally distributed, whereas the axilla, gingiva, neck, and perineum were not normally distributed. Medians (quartile 1, quartile 3) are reported for all locations for ease of comparison (Figure 3; Table 4). There was a significant difference in perineum infrared temperatures between–6.7 and 8.9 °C (P = .024), but not between indoor and–6.7 °C (P = .074) or indoor and 8.9 °C (P = .13). The number of “Lo” readings for the neck and axilla made statistical comparisons at these locations irrelevant. There was a significantly higher variance across horses in infrared temperatures obtained outside compared to indoor climate-controlled conditions for the eye (P = .002), gingiva (P = .047), and perineum (P = .005).
Data presented as box plots with overlay scatter from 10 horses showing temperature measurements at 3 different ambient temperatures (climate controlled [average, 22.1 °C],–6.7 °C, and 8.9 °C). Box plots indicate the median and quartiles, with whiskers extending to 1.5 times the IQR and dots representing each temperature reading. Color corresponds to the ambient temperature at each location (orange = climate controlled, blue =–6.7 °C, and orange = 8.9 °C).
Citation: Journal of the American Veterinary Medical Association 262, 6; 10.2460/javma.23.12.0714
Summary statistics for the rectal temperature and each infrared temperature of 10 horses in a climate-controlled environment and outdoor ambient temperatures presented as median (IQR 1–IQR 3). P value is the result of repeated-measures ANOVA or Friedman test (nonparametric) to assess effect of ambient temperature on body temperature measurements at each location.
| Anatomical location | Temperature (°C) | P value |
|---|---|---|
| Rectal | .73 | |
| Climate controlled | 37.5 (37.2–37.7) | |
| Outside (8.9 °C) | 37.2 (35.9–37.4) | |
| Outside (–6.7 °C) | 37.2 (37.1–37.7) | |
| Gingiva | .07 | |
| Climate controlled | 37.1 (37.0–37.3) | |
| Outside (8.9 °C) | 37.2 (36.9–37.3) | |
| Outside (–6.7 °C) | 38.2 (37.4–38.9) | |
| Eye | .37 | |
| Climate controlled | 36.2 (35.8–36.3) | |
| Outside (8.9 °C) | 35.4 (34.7–36.4) | |
| Outside (–6.7 °C) | 36.5 (34.4–37.8) | |
| Axilla | .05 | |
| Climate controlled | 32.0 (32.0–32.0) | |
| Outside (8.9 °C) | 32.0 (32.0–32.0) | |
| Outside (–6.7 °C) | 32.0 (32.0–32.0) | |
| Perineum | .02 | |
| Climate controlled | 36.5 (36.1–36.9) | |
| Outside (8.9 °C) | 35.4 (32–36.6) | |
| Outside (–6.7 °C) | 38.7 (37.6–39.2) | |
| Neck | .61 | |
| Climate controlled | 32.0 (32.0–32.1) | |
| Outside (8.9 °C) | 32.0 (32.0–32.0) | |
| Outside (–6.7 °C) | 32.0 (32.0–32.0) |
Discussion
As expected, noncontact temperature readings from an infrared thermometer were not the same as rectal temperature using a digital thermometer in the study population, with the infrared temperature readings on average 0.5 to 3.37 °C lower than rectal temperatures depending on location. This finding agrees with previously published studies that have directly compared infrared thermometer readings to traditionally obtained body temperature (rectal or oral). However, the repeatability of the infrared thermometer, indicated by the extremely low CV for infrared temperature measurement at each body location in our study, suggested that the infrared thermometer may still be a reliable tool if applied with realistic expectations. It is reasonable to postulate that with a correction factor or appropriate reference range, the infrared thermometer can be used in a clinical setting.
Measurements at the eye and perineum were both moderately positively correlated with rectal temperatures and were highly repeatable, supporting the computation of reference ranges for these sites in a climate-controlled environment. In our population, the reference range for rectal temperature was 36.7 to 38.6 °C, which corresponds with well-established clinical reference ranges.1 The infrared thermometer reference ranges were 36 to 37.8 °C for the perineum and 35.7 to 37.1 °C for the eye. These reference ranges are corroborated by the results of the Bland-Altman analysis, which demonstrated a bias of 0.77 °C for the perineum and 1.23 °C for the eye, with a range of agreement of < 1.9 °C at each location. This analysis supports adding a correction factor of 0.77 or 1.23 °C to a temperature measurement obtained at the perineum or eye, respectively. A similar concept is applied in pediatric medicine when obtaining an axillary temperature by adding 1 degree as an estimate of oral temperature.15–17 This correction factor is similar to a previous report9 in horses in which the authors reported infrared temperatures of haired areas had a bias of 0.95 °C compared to rectal temperature. However, in contrast to this previous report, our data did not support the use of haired locations for infrared temperature measurement. In our study population, infrared temperature measurements at the neck and axilla were not significantly correlated with rectal temperature and were biased by more than 3 °C. The most likely explanation for the difference in our findings is the distinctly different environments in which the studies were performed. In the previous report, infrared temperatures were measured during the day in outside ambient temperatures of 25 to 26.7 °C, while our study population was either indoors at a climate-controlled 22.1 °C or outdoors at < 10 °C. Further investigation regarding the effect of ambient temperature on infrared thermometer measurements is warranted.
The repeatability and calculation of reference ranges for the perineum and eye infrared temperatures make these reasonable alternative locations in horses that are intractable to rectal temperature measurement. It is not surprising that the perineal temperature would be closer to the rectal temperature given its relatively protected location beneath the tail when compared to the exposed eye. While horses in this study subjectively were much more tolerant of infrared temperature measurement at the perineum than rectal temperature measurement, the eye may be preferred if safety near the hind limbs is a concern.
The consistent indoor ambient temperature likely artificially enhanced the consistency of the infrared thermometer temperature readings compared to field settings. This is supported by the significantly increased variance in infrared temperatures obtained outside at both temperatures when compared to the climate-controlled conditions. The infrared thermometer manufacturer states that the instrument should be used in temperatures ranging from 10 to 40 °C, which makes its use outdoors in winter conditions problematic.18 In the study reported here, outdoor ambient temperatures had a significant effect on the infrared temperature obtained at the perineum but not the globe. Therefore, the calculated reference ranges cannot be applied when obtaining an infrared perineal temperature at the 2 outside ambient temperatures reported in this study. However, infrared temperature measurement at the eye is still applicable and places the equine practitioner at less risk of hind limb kick.
Limitations of this study include the climate-controlled environment and relatively small number of horses in the study used to evaluate the effect of outside ambient temperatures. Another study with a larger sample size would be required to determine suitable reference ranges at the perineum under different ambient conditions. Sample size for outdoor temperature measurements was limited by the horses available and housing conditions. Times of data collection were also limited to personnel availability, which occurred primarily in the winter months and resulted in many horses presenting with longer hair coats. The repeatability and clinical utility of the infrared thermometer has yet to be determined in warmer temperatures. All infrared temperatures were obtained by a single individual; measurement by multiple individuals may result in greater variability and less repeatability. It may be beneficial to evaluate interobserver agreement prior to implementing infrared thermometer use in a larger setting. Additionally, the proposed reference ranges for the eye and perineum under climate-controlled conditions should be validated in an independent population of afebrile horses. The inclusion criteria for this preliminary study limited the population to afebrile horses (as judged by rectal temperature) and horses greater than 1 year of age. To establish true clinical utility of the proposed infrared temperature sites (perineum and eye), additional evaluation in febrile and systemically ill horses should be pursued as well as foals younger than 1 year.
In conclusion, while an infrared thermometer temperature is not numerically the same as a rectal temperature using a digital thermometer, measurements at the perineum and eye are significantly correlated with rectal temperature readings. Further, the repeatability of infrared readings allows for establishment of reference ranges and proposal of reasonable correction factors that makes infrared temperature measurement a practical tool under certain conditions when patient compliance and safety are a concern. Based on our findings, when used outdoors in cooler ambient temperatures, infrared temperature readings at the eye would be recommended over the perineum. Although a digital rectal temperature remains the gold standard used to assess temperature in a clinical setting, additional validation of the use of an infrared thermometer in horses is warranted.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org.
Acknowledgments
None reported.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.
Funding
The authors have nothing to disclose.
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