Background: Serum symmetric dimethylarginine (SDMA) is used to screen for renal dysfunction in dogs. The gold standard technique for measuring SDMA, liquid chromatography-tandem mass spectrometry (LC-MS/MS) is not widely available. Age-specific reference intervals for SDMA in older dogs are lacking. Objectives: Prospective study in older dogs to validate a commercially available LC-MS/MS method for SDMA, compare SDMA concentrations with concentrations measured using ELISA and obtain a reference interval (RI) for older dogs using both methods. Animals: Client-owned older dogs undergoing health screening. Methods: The LC-MS/MS method was analytically validated (limit of detection, precision, and linearity). Serum was sent cooled overnight for ELISA or was frozen at −80°C until batch analysis using LC-MS/MS. Results of LC-MS/MS and ELISA were compared and RIs for older dogs were calculated according to international guidelines. Results: The LC-MS/MS method showed good linearity (r2 = .99) and precision (coefficient of variation <10%), with a laboratory RI between 8.0 and 14.0 μg/dL. Paired measurements were available from 118 different dogs. Median SDMA concentration were 9.4 (range, 5.0-21.2) using LC-MS/MS and 12.0 (range, 5.0-22.0) μg/dL using ELISA. Both methods significantly differed with a mean difference of 2.2 μg/dL. The RI for older dogs for LC-MS/MS was 4.4-15.0 μg/dL, and for ELISA was 6.4-17.4 μg/dL. Conclusions and Clinical Importance: The ELISA provided significantly higher SDMA concentrations compared to the validated LC-MS/MS method, indicating the need for device- or assay-specific RI. The obtained age-specific RI for SDMA is considerably higher in older dogs compared to the general laboratory RI.

Background: Up to 25% of elderly humans have proteinuria, often associated with underlying lesions. Data concerning the presence of proteinuria in elderly dogs is scarce. Objectives: To describe the presence and persistence of proteinuria and to compare urinary protein : creatinine ratio (UPC) between free catch and cystocentesis urine samples in apparently healthy elderly dogs. Animals: Hundred apparently healthy elderly dogs. Methods: Prospective study. Owners of 100 elderly dogs were asked to collect 2 free catch urine samples. Dogs were considered healthy based on owner's perception and an age chart, based on ideal bodyweight, was used to define dogs as senior or geriatric. UPC of urine collected by free catch and cystocentesis were compared. Overt proteinuria and borderline proteinuria were defined as UPC >0.5 and between 0.2 and 0.5, respectively, if examination of sediment did not explain proteinuria. Proteinuria was considered persistent if present at both sampling times. Results: At baseline, 71 owners succeeded in collecting urine. Eleven percent of dogs had overt proteinuria, 14% were borderline proteinuric, and 75% nonproteinuric. Thirty-seven repeated urine samples, with a median time interval of 31 days (range 10–90), were available. Nineteen percent of dogs had a persistently increased UPC (>0.2), with persistent overt proteinuria present in 8%. A strong correlation (ρ = 0.88) was found between UPC of urine collected by free catch and cystocentesis. Conclusions and Clinical Importance: As 19% of study dogs had persistent proteinuria, our findings emphasize that measurement of proteinuria should be part of geriatric health screening. For UPC in dogs, free catch urine provides a good alternative to cystocentesis.

Background: Urinalysis is necessary for the diagnostic evaluation of chronic kidney disease in cats. Performing cystocentesis is not always feasible, but data comparing urine obtained by cystocentesis in the clinic with voided samples collected at home are lacking in cats. Objectives: To compare urinary protein:creatinine ratio (UPC) and urine specific gravity (USG) and to detect clinically relevant changes in proteinuria substage or urine concentration between urine collected at home and in-clinic by cystocentesis in cats. Animals: Ninety-two healthy and diseased client-owned cats. Methods: Prospective study. Owners collected voided urine at home and within 1 to 15 hours, cystocentesis was performed in the clinic. Results: In a subset of motivated owners, 55% succeeded in collecting urine at home. Overall, UPC was higher (mean ±SD difference = 0.09 ±0.22; P < .001) and USG was lower (mean ±SD difference = −0.006 ±0.009; P < .001) in cystocentesis samples than in voided urine. Substantial agreement existed between sampling methods for UPC (weighted к = 0.68) and USG (к = 0.64) categories. A different proteinuria substage (UPC < 0.2, 0.2-0.4, >0.4) was present in paired urine samples from 28% of cats. In 18% of cats, urine concentrating ability (USG < or ≥1.035) differed between both samples. Conclusions and Clinical Importance: Home sampling of urine is a valid alternative to cystocentesis in cats. However, because clinically relevant differences in UPC and USG were present in 28% and 18% of cats, respectively, by the same collection method for monitoring each cat is advised.

Background: Although regular health screening is recommended, long-term follow-up data in healthy aged cats are lacking. Objectives: Determine the most common conditions in a large group of apparently healthy older cats and which diseases are manifested within 2 years in cats confirmed to be healthy based on extensive health screening. Animals: Client-owned cats. Methods: Prospective study. Thorough history, physical examination, blood tests, and urinalysis were performed in 259 apparently healthy mature adult (7-10 years) and senior (>10 years) cats. Semi-annual follow-up examinations were performed in 201 confirmed healthy cats. Results: At baseline, 21% of apparently healthy cats were not considered healthy but were diagnosed with International Renal Interest Society (IRIS) ≥ stage 2 chronic kidney disease (CKD; 7.7%) or hyperthyroidism (4.6%), among other disorders. Disease occurred significantly more frequently in senior cats compared with mature adult cats. In addition, 40% cats were overweight, 35% had moderate to severe dental disease, and 22% had abnormal cardiac auscultation findings. Within 2 years, 28% of mature adult and 54% of senior cats that were confirmed healthy at inclusion developed new diseases, most commonly IRIS ≥ stage 2 CKD (cumulative incidence, 13.4%), hyperthyroidism (8.5%), chronic enteropathy, hepatopathy or pancreatitis (7.5%), or neoplasia (7%). Conclusions and Clinical Importance: The high prevalence and 2-year incidence of physical examination abnormalities and systemic diseases in apparently healthy older cats argue for regular health screening in cats ≥7 years of age. Although more common in senior cats, occult disease also occurs in mature adult cats, and owners should be informed accordingly.

Background: Stability of serum symmetric dimethylarginine (sSDMA) during short- and long-term storage has not been assessed for the immunoassay of the Point-of-Care IDEXX Catalyst DX (POC) analyzer and the Enzyme Multiplied Immunoassay Technique of IDEXX commercial laboratory (CL). Also, the agreement between both analyzers is questioned. Objectives: To determine (a) the effect of storage time and temperature on sSDMA measured by POC and CL; (b) the agreement between sSDMA measured by POC and CL; and (c) the imprecision of the POC. Animals: Serum of cats (n = 17) and dogs (n = 18) with a range of SDMA concentrations (6 to >100 μg/dL). Methods: Based on an equivalence trial with predefined equivalence range (−3.0 to +3.0 μg/dL) and using T0 as baseline, stability was evaluated after 24 hours at 22°C and 4°C (POC); after 7 days at 4°C (POC and CL) and after 10 and 24 months at −24°C and −80°C (CL). Bland-Altman plots enabled method comparison. Imprecision of the POC was assessed by duplicate sSDMA measurements at T0. Results: The POC analyzer produced equivalent sSDMA measurements if samples were stored for 24 hours at 4°C (95% confidence interval [CI]: −2.5-2.0 μg/dL), but not when stored for 24 hours at room temperature (RT; 95% CI: −4.1 to 0.5 μg/dL) or after 7 days at 4°C (95% CI: −3.6-1.0 μg/dL). The CL analyzer was less affected by preanalytical variation with clinically similar results obtained when samples were stored for 7 days at 4°C (95% CI: −2.2 to 2.4 μg/dL) and for at least 24 months at −24°C (95% CI: −1.7 to 2.9 μg/dL) and −80°C (95% CI: −1.5 to 3 μg/dL). A relevant mean difference of −2.3 μg/dL between both analyzers was found. Duplicate POC measurements were equivalent (95% CI: −2.6 to 2.0 μg/dL). Conclusions: Delayed analysis may significantly change sSDMA depending on storage and measurement conditions. Interchangeable use of assays should be done with caution because analytical variation could be interpreted as clinically relevant change.