Longitudinal Study of Microalbuminuria
in Soft Coated Wheaten Terriers
S Vaden1, W Jensen2, S Longhofer2, DF Simpson2
1. North Carolina State University, Raleigh NC;
2. Heska Corporation, Fort Collins CO
Presented at 19th Annual Veterinary Medical Forum, Denver, May 2001;
Published in the Journal of Veterinary Internal Medicine, 2001, 15:300.

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Microalbuminuria (MA) is defined as the presence of low concentrations of albumin in the urine, which are below the limit of detection using standard urine dipsticks. Persistent MA may be indicative of glomerular injury or disease. Protein-losing nephropathy (PLN) of Soft Coated Wheaten Terriers (SCWT) is due to a glomerular disease. Therefore, we hypothesized that MA would be detected in affected SCWT early in the disease process, before the onset of overt proteinuria as detected by urine dipstick, routine urinalysis or urine protein:creatinine ratio.

In this study, we measured urine albumin concentrations (using an antigen capture ELISA) in urine samples that were obtained from all dogs in our colony. Because urine concentration influences our interpretation of urine protein content (hence the need for setting up a ratio of protein to creatinine), all urine samples were adjusted to a standard concentration (specific gravity of 1.010) prior to measurement of urine albumin.

Of 17 dogs in our colony from which a sufficient number of urine samples were available, 13 had MA detected in at least one sample. Half of the dogs had MA present in at least 50% of their samples. Urine albumin concentrations increased with advancing age. Three of the 13 dogs with MA proceeded to develop overt albuminuria (i.e., >30 mg/dl, a concentration that should be detectable using standard methods of urine protein detection). Two of these 3 dogs had abnormal urine protein:creatinine ratios. In these 2 dogs, MA and the abnormal urine protein:creatinine ratio were detected at the same time. However, MA preceded the onset of an abnormal urine protein:creatinine ratio by 1 year in the remaining dog.

This study demonstrated that the prevalence of MA is high in the SCWT and SCWT crosses that are in our colony and that in some of these dogs MA preceded the onset of abnormal urine protein:creatinine ratios. More study is needed to determine if remaining dogs in this study that have MA but did not have abnormal protein:creatinine ratios progress to develop PLN.

We now have 8 dogs that have developed abnormal urine protein:creatinine ratios. In 4 of these dogs, MA was noted before urine protein:creatinine ratios became abnormal (by as much as 27 months), and in 2 of these dogs MA and abnormal urine protein:creatinine ratios were noted at the same time. Persistent MA appears to be a good indicator of glomerular injury, and therefore PLN, in SCWT.

Urine albumin concentrations need to be evaluated on a regular basis for the following reasons: 1) physiologic changes may cause transient MA, 2) dogs that have normal urine albumin concentrations could develop MA as glomerular injury progresses, and 3) persistent MA may indicate PLN of SCWT or another form of glomerular disease.

Urine albumin can be measured in SCWT using one of two means. The first is to ask you veterinarian to use a new test called the ERD-ScreenTM Urine Test (Heska Corporation, Denver CO). This test is a semi-quantitative test that will tell your veterinarian if your dog's urine has albumin concentrations that are below threshold (within the expected range for a normal dog) or above threshold (consistent with MA). You can find out more about this test by going to the following web site: www.heska.com/erdscreen/index.asp. The advantage of using this test is that it is an in-clinic test and you can find out the results quickly.

If the test result is positive, you can send a urine sample to me and I will process it for quantification of the urine albumin concentration. If your dog has a negative test result, I STILL WANT TO HEAR ABOUT IT! If I only hear about the abnormal results, the prevalence data that I generate will be erroneous. Alternatively, you can send a urine sample to me and I will process the sample with the understanding that there will be a delay before you receive the results. Send all results to Dr. Shelly Vaden, North Carolina State University, College of Veterinary Medicine, 4700 Hillsborough Street, Raleigh NC 27606. Send samples to Tonya Harris at the same address.

 

JVIM 2001 15:300


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