Early recognition and rapid induction of treatment are critical to reducing morbidity and mortality in diabetic cats that become ketoacidotic.Urine dipstick is the standard means for detecting ketone bodies in diabetic cats.The plasma ketone dip test (PKDT) using the urine dipstick colorimetric method was introduced in 2003. In this study, the results of the urine ketone dipstick test (UKDT) and PKDT in cats with possible ketosis or diabetic ketoacidosis (DKA) were compared, with plasma beta-hydroxybutyrate (beta-OHB) measurements used as the gold standard.On the basis of clinical examination findings, beta-OHB measurements, and blood gas analysis, 54 cats with diabetes mellitus were classified into 1 of 3 groups: nonketotic cats (n= 3), ketotic cats (n = 40), or ketoacidotic cats (n = 11). Paired urine and blood samples were collected, and urine and plasma were both tested on urine ketone reagent strips to determine acetoacetate concentrations. Although a good correlation was found between blood and urine ketone measurements, the results differed significantly—measurements of the PKDT were on average higher than results of the UKDT.The best cutoff values for detecting ketoacidosis was 1+ (≥ 1.5 mmol/L) for urine and 2+ (≥ 4 mmol/L) for plasma.Using these cutoff values yielded the following sensitivities and specificities: 82% and 95% for urine and 100% and 88% for plasma, suggesting that PKDT is a useful tool for ruling out DKA.Because of its higher sensitivity, the PKDT performs better than the UKDT in identifying cats with impending or established ketoacidosis.

COMMENTARY: It is very interesting that so many cats were found to be positive for beta-OHB even though they did not have metabolic acidosis.As highlighted by the authors, hospitalization is typically recommended for cats with ketosis because it is a signal that other serious metabolic derangements are present.The high proportion of cats without acidosis in this study might appear to contradict this. To clarify these findings, it is important to review some aspects of ketone metabolism and sampling. First, ketones are a normal source of energy for the body.The main ketones produced by the body are acetone, beta-OHB, and acetoacetate (which also explains the characteristic odor). Urine and plasma dipsticks measure the presence of acetoacetate, whereas the serum test used measures beta-OHB. Second, it is only in the absence of insulin (decreasing glucose availability) and presence of diabetogenic hormones (increasing fatty acid oxidation) that the body’s ability to handle these ketones is exceeded, leading to their increased presence in serum and thus urine.The disparity seen in this study could represent a normal physiologic shift during the development of ketoacidosis.Also of note is that during the treatment and resolution of ketoacidosis, the type of ketone may shift, resulting in an initial increase in the patient’s positivity.This change does not necessarily represent deterioration.These authors confirmed that plasma
samples can be used to confirm the presence of ketones in diabetic patients in which urine samples cannot be obtained on presentation. Because we frequently obtain packed cell volume/total solids as part of our quick assessment of sick patients and we usually need 2 samples to run the test,we can now use the second sample to assess for ketones. In addition to helping us make treatment decisions for our patients, it helps us establish whether ketones are present.That information is valuable because the prognosis for hyperosmolar nonketotic diabetes mellitus is considered worse than that for DKA.—Nyssa Reine, DVM, Diplomate ACVIM (Internal Medicine)

Ketone measurements using dipstick methodology in cats with diabetes mellitus. Zeugswetter F, Pagitz M. J SMALL ANIMPRACT 50:4-8, 2009.