Objective—To compare 2 methods for estimation of glomerular filtration rate (GFR), study the effects of age and body size on GFR estimates, and provide a reference range for estimated GFR in clinically normal cats.
Procedures—In each cat, GFR was estimated via plasma clearance of iohexol and creatinine. Results of a 1-compartmental model (CL1comp) were calibrated to a trapezoidal method estimate (CLtrap) by use of a correction formula applicable to dogs or humans and standardized to body weight; for iohexol clearance, data were also standardized to extracellular fluid volume (ECFV). For all 57 cats, method comparison was performed via agreement analysis. Reference ranges for GFR derived by the different methods were established by use of data from a subset of 51 cats after exclusion of 6 cats that were azotemic, Birman, or both.
Results—In 57 cats, mean CLtrap of creatinine was 0.29 mL/min/kg (13%) higher than CLtrap of iohexol. In 51 nonazotemic cats, mean CLtrap was 2.26 mL/min/kg for iohexol (reference range, 1.02 to 3.50 mL/min/kg) and 2.55 mL/min/kg for creatinine (reference range, 1.27 to 3.83 mL/min/kg). Values of GFR/kg or GFR standardized to liters of ECFV did not decrease with increasing age. A negative linear relationship was detected between body weight and estimated GFR/kg or GFR standardized to liters of ECFV.
Conclusions and Clinical Relevance—Reference ranges for estimated GFR via plasma clearance of iohexol and creatinine should facilitate early detection of impaired renal function in cats, although body weight should be taken into account.
Objective—To determine the degree of agreement between 3 commercially available point-of-care blood glucose meters and a laboratory analyzer for measurement of blood glucose concentrations in Hispaniolan Amazon parrots (Amazona ventralis).
Procedures—A 26-gauge needle and 3-mL syringe were used to obtain a blood sample (approx 0.5 mL) from a jugular vein of each parrot. Small volumes of blood (0.6 to 1.5 μL) were used to operate each of the blood glucose meters, and the remainder was placed into lithium heparin microtubes and centrifuged. Plasma was harvested and frozen at −30°C. Within 5 days after collection, plasma samples were thawed and plasma glucose concen-trations were measured by means of the laboratory analyzer. Agreement between pairs of blood glucose meters and between each blood glucose meter and the laboratory analyzer was evaluated by means of the Bland-Altman method, and limits of agreement (LOA) were calculated.
Results—None of the results of the 3 blood glucose meters agreed with results of the laboratory analyzer. Each point-of-care blood glucose meter underestimated the blood glucose concentration, and the degree of negative bias was not consistent (meter A bias, −94.9 mg/dL [LOA, −148.0 to −41.7 mg/dL]; meter B bias, −52 mg/dL [LOA, −107.5 to 3.5 mg/dL]; and meter C bias, −78.9 mg/dL [LOA, −137.2 to −20.6 mg/dL]).
Conclusions and Clinical Relevance—On the basis of these results, use of handheld blood glucose meters in the diagnosis or treatment of Hispaniolan Amazon parrots and other psittacines cannot be recommended.
Objective—To develop and validate a gas chromatography–mass spectrometry (GC-MS) method for determination of Nτ-methylhistamine (NMH) concentration in canine urine and fecal extracts and to assess urinary NMH concentrations in dogs with mast cell neoplasia and fecal NMH concentrations in dogs with protein-losing enteropathy.
Sample Population—Urine specimens were collected from 6 healthy dogs and 7 dogs with mast cell neoplasia. Fecal extracts were obtained from fecal specimens of 28 dogs with various severities of protein-losing enteropathy, as indicated by fecal concentration of α1-proteinase inhibitor.
Procedures—NMH was extracted directly from urine, and fecal specimens were first extracted into 5 volumes of PBSS containing 1% newborn calf serum. Nτ-methylhistamine in specimens was quantified via stable isotope dilution GC-MS. The assay was validated via determination of percentage recovery of known amounts of NMH and interassay coefficients of variation. Urinary excretion of NMH was evaluated by means of NMH-to-creatinine concentration ratios.
Results—Recovery of NMH in urine and fecal extracts averaged 104.6% and 104.5%, respectively. Interassay coefficients of variation ranged from 5.4% to 11.7% in urine and 12.6% to 18.1% in fecal extracts. Urinary NMH excretion was significantly increased in dogs with mast cell neoplasia, compared with that in healthy dogs. No correlation was detected between severity of protein-losing enteropathy and fecal NMH concentration.
Conclusions and Clinical Relevance—This method provided a sensitive, reproducible means of measuring NMH in canine urine and fecal extracts. High urinary NMH-to-creatinine concentration ratios in dogs with mast cell neoplasia are consistent with increased histamine release in this disease.
Objective—To determine the optimal sample handling and processing conditions for the carbon 13 (13C)-labeled aminopyrine demethylation blood test (ADBT; phase 1) and determine the reference range for test results (phase 2) in apparently healthy dogs.
Procedures—In phase 1, a blood sample from each dog was collected before and 45 minutes after (day 0) IV administration of 13C-labeled aminopyrine (2 mg/kg); aliquots were immediately transferred into tubes containing sodium heparin and hydrochloric acid (samples A and B), sodium heparin alone (samples C, D, and E), or sodium fluoride (sample F). Hydrochloric acid was added to samples C through F at days 7, 14, 21, and 21, respectively. The baseline and 45-minute samples' absolute 13C:12C ratios were determined via fractional mass spectrometry on day 0 (control sample A) or 21 (samples B through F) and used to calculate the percentage dose of 13C recovered in CO2 extracted from samples (PCD). In phase 2, blood samples from each dog were collected into tubes containing sodium fluoride and processed within 3 weeks.
Results—Compared with the control sample value, PCDs for samples C through E differed significantly, whereas PCD in sample F did not. The 13C-ADBT–derived PCD reference range (central 95th percentile) for apparently healthy dogs was 0.08% to 0.2%.
Conclusions and Clinical Relevance—Glycolytic CO2 production in canine blood samples collected during 13C-ADBTs was sufficiently inhibited by sodium fluoride to allow delayed sample analysis and avoid transportation of hydrochloric acid–treated samples.
Objective—To develop and analytically validate a radioimmunoassay (RIA) for the quantification of canine calprotectin (cCP) in serum and fecal extracts of dogs.
Sample Population—Serum samples (n = 50) and fecal samples (30) were obtained from healthy dogs of various breeds and ages.
Procedures—A competitive, liquid-phase, double-antibody RIA was developed and analytically validated by assessing analytic sensitivity, working range, linearity, accuracy, precision, and reproducibility. Reference intervals for serum and fecal cCP concentrations were determined.
Results—Sensitivity and upper limit of the working range were 29 and 12,774 μg/L for serum and 2.9 and 1,277.4 μg/g for fecal extracts, respectively. Observed-to-expected ratios for serial dilutions of 6 serum samples and 6 fecal extracts ranged from 95.3% to 138.2% and from 80.9% to 118.1%, respectively. Observed-to-expected ratios for spiking recovery for 6 serum samples and 6 fecal extracts ranged from 84.6% to 121.5% and from 80.3% to 132.1%, respectively. Coefficients of variation for intra-assay and interassay variability were < 3.9% and < 8.7% for 6 serum samples and < 8.5% and < 12.6% for 6 fecal extracts, respectively. Reference intervals were 92 to 1,121 μg of cCP/L for serum and < 2.9 to 137.5 μg of cCP/g for fecal extracts.
Conclusions and Clinical Relevance—The RIA described here was analytically sensitive, linear, accurate, precise, and reproducible for the quantification of cCP in serum and fecal extracts. This assay should facilitate research into the clinical use of serum and fecal cCP measurements in dogs with inflammatory bowel disease.
Objective—To evaluate whether changes in myoelectrical activity in the cecum and large colon of horses can be detected via multichannel electrointestinography (EIG).
Animals—6 healthy mature horses.
Procedures—Each horse underwent 3 EIG procedures. Intestinal myoelectrical activity (cecum and large colon) was recorded during a 20-minute period following IV administration of physiologic saline (0.9% NaCl) solution (20 mL; baseline), erythromycin lactobionate (0.5 mg/kg), or detomidine (0.015 mg/kg); intestinal contractions were concurrently viewed via B-mode ultrasonography. By use of computer software, 8-channel EIG recordings were analyzed and the mean of the dominant frequency (a measure of the rhythmicity of gastric electrical activity) expressed in cycles per minute (cpm) was obtained. Total power (MV2) was calculated, and treatment effect was expressed as the power ratio (ie, treatment-associated power divided by the baseline power).
Results—The dominant frequency cpm values were not stable, and no significant differences between treatments were detected. Compared with the effects of saline solution treatment, detomidine significantly reduced the mean cecal and colonic power ratios. Erythromycin significantly reduced the cecal power ratio and increased the colonic power ratio, although the increase was significant in only 1 channel. Ultrasonographic findings and total power (predominantly from the long-distance electrode pairs) were significantly correlated.
Conclusions and Clinical Relevance—In horses, EIG was useful for assessment of changes in myoelectrical activity in the cecum and large colon. Multiple electrodes should be used to cover a larger area of the intestine, and agreement between multiple channels is needed to make the analysis meaningful.
Objective—To determine cytologic and microbiologic findings in bronchoalveolar lavage (BAL) fluid and SpO2 values obtained during BAL in healthy rabbits.
Procedures—Bronchoscopic BAL of left and right caudal lobar bronchi (LB2 and RB4) was performed with 3 mL of sterile saline (0.9% NaCl) solution; SpO2 was measured before, during, and after BAL. Percentage fluid recovered, total leukocyte counts, and differential cell counts were determined. Aerobic and anaerobic bacterial, mycoplasmal, and fungal cultures were performed from combined LB2 and RB4 samples.
Results—Mean ± SD percentage fluid volumes recovered from LB2 and RB4 were 53 ± 13% and 63 ± 13%, respectively. Mean ± SD total leukocyte counts from LB2 and RB4 were 422 ± 199 cells/μL and 378 ± 97 cells/μL, respectively. Macrophages were most frequently identified. There were no significant differences in volumes retrieved, total leukocyte counts, or differential cell percentages between LB2 and RB4. Microbial culture results were negative for 3 rabbits and positive for mixed aerobic and anaerobic bacterial growth in 6 and 2 rabbits, respectively. The SpO2 was ≥ 95% in 7 of 9 rabbits after anesthetic induction, < 95% in 5 of 6 rabbits 1 minute after BAL, and ≥ 95% in 5 of 9 rabbits and > 90% in 4 of 9 rabbits 3 minutes after BAL.
Conclusions and Clinical Relevance—Bronchoscopic BAL with 3 mL of saline solution provided adequate fluid recovery for microbiologic and cytologic examination from the caudal lung lobes. Transient low SpO2 was detected immediately after BAL.
Objective—To determine the characteristics of an automated canine C-reactive protein (CRP) assay and evaluate 2 human CRP assays for use in dogs.
Animals—56 client-owned dogs with pyometra and 11 healthy control dogs.
Procedures—Samples from 11 dogs with high (> 100 mg/L) or low (< 10 mg/L) CRP concentrations (determined by use of a canine ELISA) were evaluated by use of the automated canine CRP assay. Intra- and interassay imprecision was determined (by use of those 2 plasma pools), and assay inaccuracy was assessed by use of logistic regression analysis of results obtained via ELISA and the automated canine CRP assay. Two automated human CRP assays were used to measure plasma CRP concentration in 10 dogs.
Results—By use of the ELISA, mean ± SD plasma CRP concentration was 96.1 ± 38.5 mg/L and 10.1 ± 23.2 mg/L in dogs with pyometra and control dogs, respectively. The automated canine assay had intra-assay coefficients of variation (CVs) of 7.8% and 7.9%, respectively, and interassay CVs of 11.1% and 13.1%, respectively. Results from the automated assay were highly correlated with results obtained via ELISA. The human assay results did not exceed 0.4 mg/L in any dog.
Conclusions and Clinical Relevance—The automated canine CRP assay had less interassay imprecision, compared with the ELISA. The 2 human CRP assays were not suitable for analysis of canine plasma samples. The automated canine CRP assay was more precise than the ELISA for serial evaluations of plasma CRP concentration in dogs.
Objective—To determine the sources and handlingof losses to follow-up (LTF) in parallel-group randomized clinical trials (RCTs).
Sample Population—63 parallel-group RCTs of > 24 hours' duration published from January 2000 through December 2005.
Procedures—Journals were hand searched for eligible reports. Details concerning the presence, cause, and amount of LTF; statistical handlingof data missingbecause of LTF; type of analyses performed; number of animals randomly allocated and analyzed; and the acknowledgement of the potential impact of LTF were recorded.
Results—In 81% (51/63) of trials, LTF were reported. In 80% (41/51) of those studies, losses in the analysis were ignored, and in only 18% (9/51) was the potential impact of LTF on study results acknowledged. Of the 47 studies in which sources of LTF were reported, 72% had loss of subjects because of investigator withdrawals, 30% because of deaths, and 26% because of owner withdrawals. Median loss of subjects for those studies was 12% because of investigator withdrawal (range, 2% to 52%), 8% because of death (1% to 28%), and 4% because of owner withdrawal (2% to 33%).
Conclusions and Clinical Relevance—Most RCTs had LTF, most of which were attributable to investigators removing randomly allocated animals from the study. In most studies, data from animal LTF were ignored and, therefore, only a subgroup of randomly allocated subjects was included in the data analysis. Most reports did not address the potential for a postrandomization selection bias associated with ignoring LTF and did not acknowledge the potential impact of the missingdata on their results.
Objective—To purify neutrophil elastase (NE) from dog blood and develop and validate an ELISA for the measurement of canine NE (cNE) in canine serum as a marker for gastrointestinal tract inflammation.
Sample Population—Neutrophils from 6 dogs immediately after they were euthanatized and serum from 54 healthy dogs.
Procedures—cNE was purified from blood by use of dextran sedimentation, repeated cycles of freezing-thawing and sonication, cation-exchange chromatography, and continuous elution electrophoresis. Antibodies against cNE were generated in rabbits, and an ELISA was developed and validated by determination of sensitivity, dilutional parallelism, spiking recovery, intra-assay variability, and interassay variability. A reference range was established by assaying serum samples from the 54 healthy dogs and by use of the lower 97.5th percentile.
Results—cNE was successfully purified from blood, and antibodies were successfully generated in rabbits. An ELISA was developed with a sensitivity of 1,100 μg/L. The reference range was established as < 2,239 μg/L. Ratios of observed-to-expected results for dilutional parallelism for 4 serum samples ranged from 85.4% to 123.1%. Accuracy, as determined by spiking recovery, ranged from 27.1% to 114.0%. Coefficient of variation for 4 serum samples was 14.2%, 16.0%, 16.8%, and 13.4%, respectively, for intra-assay variability and 15.4%, 15.0%, 10.5%, and 14.6%, respectively, for interassay variability.
Conclusions and Clinical Relevance—The purification protocol used here resulted in rapid and reproducible purification of cNE with a high yield. The novel ELISA yielded linear results and was accurate and precise. Additional studies are needed to evaluate the clinical usefulness of this assay.