CANINE-Hematologic and Serum Biochemical Reference Values in Retired Greyhounds

Vol. 22, No. 3 March 2000

CE

V

Refereed Peer Review

FOCAL POINT ★ Reference ranges for certain hematologic and serum biochemical values in retired greyhounds differ from those of the general canine population.

Hematologic and Serum Biochemical Reference Values in Retired Greyhounds

KEY FACTS Auburn University ■ The number of greyhounds in private homes (55,000+) is approaching the number of racing greyhounds in the United States (approximately 75,000). ■ More than 50% of 50 retired greyhounds had values outside the standard reference range for hemoglobin, creatinine, globulin, sodium, total carbon dioxide, and anion gap. ■ Platelet and leukocyte counts tended to be at the low end of the reference range, whereas hematocrit and total bilirubin tended to be at the high end. ■ Practitioners need clinical pathology reference ranges for this breed because greyhound values cannot be strictly compared to standard canine reference ranges.

Janet E. Steiss, DVM, PhD William G. Brewer, Jr., DVM Elizabeth Welles, DVM, PhD James C. Wright, DVM, PhD ABSTRACT: Research has indicated that results of blood tests for retired greyhounds may fall outside the established normal ranges for the general canine population and that specific parameters for retired greyhounds may need to be established. Based on the study discussed in this article, the authors determined that hemoglobin, creatinine, sodium, total carbon dioxide, and anion gap tend to be elevated whereas globulin tends to be decreased in healthy retired greyhounds. Practitioners need to be aware of these breed-specific differences in order to make accurate diagnoses in greyhounds.

T

he demographics of the greyhound population in the United States is changing: It is estimated that more than 55,000 greyhounds live in private homes compared with approximately 75,000 on racetracks.a In 1996, there were 18,000 new private adoptions. Specific reference ranges for hematologic and serum biochemical values for retired greyhounds need to be established. Veterinarians working with racing greyhounds consider that this breed tends to have relatively higher values for erythrocytes, bicarbonate, and urea and relatively lower values for leukocytes, globulin, calcium, and cholesterol.1 Most previously reported values have been measured in small groups of racing greyhounds2,3 or immature or breeding greyhounds,3 or the authors did not state how long the dogs had been retired from the racetrack before blood samples were obtained.4,5 In the study presented here, blood samples were evaluated from 50 retired greyhounds housed for a mean of 10 weeks before blood samples were collected. aPersonal

1997.

communication: Guccione G, National Greyhound Association, Abilene, KS,

Small Animal/Exotics

Compendium March 2000

The study findings can be compared with previous reports for greyhounds.2–5 In contrast to one study2 in which the dogs were racing, their diet contained large amounts of meat, and females received intermittent testosterone injections, the dogs in the study presented here were not medicated and were fed a commercial diet more comparable to what a pet would receive (guaranteed analysis of 25% crude protein and 10% crude fat). Although the dogs in this study were not client-owned animals, the kennel facilities, diet, and exercise level could be considered to approximate a household environment. Because the turnover of erythrocytes is generally accepted to be approximately 120 days in dogs, it is unlikely that any testosterone injections administered at the racetrack influenced the results of this study. In fact, the life span of erythrocytes in greyhounds has been reported to be shorter than that in mongrel dogs (mean, 53.6 and 104.3 days, respectively).6 Female dogs in this study were housed for a mean of 14 weeks (median, 10 weeks), which exceeds the reported erythrocyte life span.

STUDY Materials and Methods Dogs Over a 2-year period, 50 mature greyhounds retired from racing were obtained from the Auburn University Department of Laboratory Animal Health. Female dogs were kenneled for a median of 10 weeks (range, 8 to 25 weeks) and male dogs for a median of 5 weeks (range, 4 to 24 weeks) before blood samples were collected. Dogs were housed in an indoor–outdoor laboratory kennel facility, fed a commercial dog food once daily, and had continuous access to filled water bowls. Dogs were negative for heartworm disease and external parasites. Dogs positive for internal parasites were dewormed with fenbendazole (1 ml/4.4 lb orally once daily for 3 days). Routine vaccinations were administered. Based on ear tattoos, dogs ranged from 1 to 3 years of age. The dogs had no clinically significant findings on physical, neurologic, and orthopedic examinations and were serologically negative for Ehrlichia canis and Ehrlichia platys. Blood Samples The average time between receiving the dogs and drawing blood samples was 10 weeks (median, 8 weeks). In addition, 10 of the study dogs were available 90 days later; blood tests were repeated to confirm initial findings. While the dogs were in their kennels, blood samples were collected via jugular venipuncture and placed into tubes containing no additives for serum

biochemistry and EDTA tubes for complete blood count analysis. Tubes of blood were packed in ice and immediately submitted to the Auburn University Clinical Pathology Laboratory.

Blood Analyses Complete blood counts were performed on an automated impedance–type instrument and included determination of erythrocyte count; hematocrit; hemoglobin concentration; total leukocyte count; platelet count; and calculation of mean corpuscular volume, mean corpuscular hemoglobin, erythrocyte distribution width, and mean platelet volume. Manual 100-cell differential counts were performed. Serum chemistry analytes were measured using a computer-assisted automated chemistry instrument. Spectrophotometric analysis included determination of (1) serum alanine transaminase, serum alkaline phosphatase, and creatine kinase activities and (2) creatinine, glucose, blood urea nitrogen, calcium, inorganic phosphate, total bilirubin, and albumin concentrations. Globulin concentration was also calculated. Concentrations of sodium, chloride, potassium, and total carbon dioxide were determined using ion-specific electrode methodology. Anion gap was calculated according to the formula: (sodium + potassium) – (chloride + total carbon dioxide). Statistics Data were entered on a spreadsheet for calculation of the mean and standard deviation values. Results Hematologic data are presented in Table I and serum biochemical data in Table II. The mean values for hemoglobin, creatinine, globulin, sodium, total carbon dioxide, and anion gap were outside the canine reference ranges for the Auburn University Clinical Pathology Laboratory. Other tendencies noted were that mean platelet and leukocyte counts were toward the low end of the reference ranges and hematocrit and total bilirubin were toward the high end. The percentage of greyhounds for which values fell outside the Auburn University reference range are presented in Figures 1 and 2. More than 50% of dogs had values outside the reference range for hemoglobin, creatinine, globulin, sodium, total carbon dioxide, and anion gap. Lower percentages of greyhounds had values above or below the reference range for several other hematologic or serum biochemistry values. Less than 5% of the 50 greyhounds in this study had any individual values outside the calculated greyhound reference ranges reported in Tables I and II.

ERYTHROCYTE LIFE SPAN ■ SERUM CHEMISTRY ANALYTES ■ ANION GAP

Compendium March 2000

Small Animal/Exotics

TABLE I Hematologic Values in Retired Greyhounds (n = 50) Laboratory Parameter Erythrocytes (×106/ml) Hemoglobin (g/dl) Hematocrit (%) Mean corpuscular volume (fl) Mean corpuscular hemoglobin (pg) Mean corpuscular hemoglobin concentration (%) Erythrocyte distribution width Platelet count (×103/ml) Mean platelet volume (fl) Leukocytes (/ml) Segmented neutrophils (/ml) Band neutrophils (/ml) Lymphocytes (/ml) Monocytes (/ml) Eosinophils (/ml)

Mean (standard deviation) 7.69 (0.85) 18.2b (1.7) 52.8 (5.7) 68.8 (2.3) 23.6 (1.0) 34.4 (0.8) 15.1 (1.0) 178 (57) 8.6 (0.9) 8200 (3200) 5494 (902) 0 (0) 1722 (738) 328 (246) 574 (492)

Greyhound a Reference Range 5.99–9.39 14.8–21.6 41.4–64.2 64–73 21.6–25.6 32.8–36.0 13.1–17.1 64–292 6.8–10.4 1800–14,600 3690–7298 — 246–3198 0–820 0–1558

AUCVM a Reference Range 5.50–8.50 12.0–18.0 37.0–55.0 60–77 19.5–24.5 32.0–36.0 11.1–17.1 160–416 6.8–9.8 6000–17,000 3000–11,400 0–300 1000–4000 150–1350 100–750

aCalculated

as two standard deviations from the mean. value outside the standard reference range. AUCVM = Auburn University College of Veterinary Medicine.

b Mean

TABLE II Serum Biochemical Values in Retired Greyhounds (n = 50) Laboratory Parameter Alanine transferase (IU/L) Serum alkaline phosphatase (IU/L) Creatine kinase (IU/L) Creatinine (mg/dl) Glucose (mg/dl) Blood urea nitrogen (mg/dl) Calcium (mg/dl) Inorganic phosphate (mg/dl) Total protein (g/dl) Albumin (g/dl) Globulin (g/dl) Total bilirubin (mg/dl) Sodium (mmol/L) Potassium (mmol/L) Chloride (mmol/L) Total carbon dioxide (mmol/L) Anion gap

Mean (standard deviation) 55 (23) 39 (18) 168 (75) 1.2b (0.2) 89 (16) 16 (3) 10 (0.7) 3.9 (0.6) 6.0 (0.6) 3.3 (0.3) 2.8b (0.7) 0.3 (0.2) 153b (2) 4.6 (0.5) 116 (3) 26.6b (6.2) 15.2b (6.0)

Greyhound a Reference Range 9–101 3–75 18–318 0.8–1.6 57–121 10–22 8.6–11.4 2.7–5.1 4.8–7.2 2.7–3.9 1.4–4.2 0.0–0.7 149–157 3.6–5.6 110–122 14.2–39.0 3.2–27.2

AUCVM a Reference Range 17–66 19–50 92–357 0.0–1.0 80–100 10–25 9.5–11.8 3.3–5.8 5.1–7.3 2.6–3.5 3.8–5.0 0.1–0.3 142–150 3.9–5.3 110–121 16.5–22.3 7.3–15.1

aCalculated

as two standard deviations from the mean. value outside the standard reference range. AUCVM = Auburn University College of Veterinary Medicine.

b Mean

Data for the 10 dogs for which blood work was repeated 90 days later are presented in Tables III and IV. Hematologic and serum biochemical values of these dogs reflect the initial tendencies found.

Discussion Compared with the standard canine reference ranges for the Auburn University Clinical Pathology Laboratory, hemoglobin, creatinine, sodium, total carbon diox-

Small Animal/Exotics

Compendium March 2000

be due to dehydration. Dehydration is also unlikely because all of the dogs lacked Mean AUCVM clinical signs of dehydration Laboratory Parameter (standard deviation) Reference Range and had free access to water 5.50–8.50 8.44 (1.22) Erythrocytes (×106/ml) and access to temperature12.0–18.0 19.1a (2.2) Hemoglobin (g/dl) controlled housing; further56.4a (7.2) 37.0–55.0 Hematocrit (%) more, bloods samples were 67 (2.3) 60–77 Mean corpuscular volume (fl) collected at various times 22.7 (1.1) 19.5–24.5 Mean corpuscular hemoglobin (pg) throughout the year. 32.0–36.0 Mean corpuscular hemoglobin concentration (%) 33.9 (0.7) Measurements were per16 (2.5) 11.1–17.1 Erythrocyte distribution width formed with ion-specific elec3 171 (59) 160–416 Platelet count (×10 /ml) trodes, which measure only 8.9 (0.9) 6.8–9.8 Mean platelet volume (fl) the electrolyte concentration 8700 (2500) 6000–17,000 Leukocytes (/ml) in the aqueous phase of the 6177 (1305) 3000–11,400 Segmented neutrophils (/ml) 0 (0) 0–300 sample. A higher hematocrit Band neutrophils (/ml) 1740 (1044) 1000–4000 Lymphocytes (/ml) would effectively result in less 150–1350 174 (87) Monocytes (/ml) plasma water, and electrolytes 100–750 609 (609) Eosinophils (/ml) would be relatively increased. aMean value outside the standard reference range. However, these greyhounds AUCVM = Auburn University College of Veterinary Medicine. had elevations only in sodium, not in potassium or chloride; this finding implies that TABLE IV the dogs have a higher conSerum Biochemical Values in Retired Greyhounds (n = 10) on Day 90 centration of sodium relative Mean AUCVM to the other electrolytes comLaboratory Parameter (standard deviation) Reference Range pared with other dogs. Fur17–66 Alanine transferase (IU/L) 75a (37) ther studies would be needed 19–50 40 (17) Serum alkaline phosphatase (IU/L) to definitively document that 92–357 156 (53) Creatine kinase (IU/L) the dogs were not dehydrated. 0.0–1.0 1.3a (0.3) Creatinine (mg/dl) Previous authors have gen80–100 103a (21) Glucose (mg/dl) erally agreed that greyhounds 10–25 22 (5) Blood urea nitrogen (mg/dl) have higher hemoglobin con9.5–11.8 9.8 (0.7) Calcium (mg/dl) 6 Sullivan and ascentrations. 3.3–5.8 3.9 (0.5) Inorganic phosphate (mg/dl) sociates5 compared 36 grey5.1–7.3 5.8 (1) Total protein (g/dl) hounds (seven adopted and 2.6–3.5 3.8a (1.1) Albumin (g/dl) 2.8a (0.4) 3.8–5.0 Globulin (g/dl) 29 awaiting adoption) with 0.4a (0.2) 0.1–0.3 Total bilirubin (mg/dl) nongreyhound controls. The 155a (2) 142–150 Sodium (mmol/L) greyhounds had higher mean 5 (0.3) 3.9–5.3 Potassium (mmol/L) values for hemoglobin, hema115 (2) 110–121 Chloride (mmol/L) tocrit, mean corpuscular vol30.5a (6.1) 16.5–22.3 Total carbon dioxide (mmol/L) ume, and mean corpuscular 13.9 (4.3) 7.3–15.1 Anion gap hemoglobin but lower erythaMean value outside the standard reference range. rocyte counts, hemoglobin P50 AUCVM = Auburn University College of Veterinary Medicine. values, Hill coefficients, platelet counts, and total protein. ide, and anion gap were elevated above the reference The results of our study follow those trends, with the exrange in more than 50% of the greyhounds in this study ception that our data did not indicate a decrease in eryand globulin was below the reference range (Figures 1 throcyte counts. No other investigators have reported and 2). Some of these findings might be interpreted as decreased erythrocyte counts in greyhounds. This inconoccurring secondary to dehydration. However, the valsistency likely reflects the relatively small number of dogs ues in 10 dogs tested 90 days later confirmed the initial and differences in age in the sampled populations. Sullivan findings and indicated that the changes were unlikely to and associates5 did not report serum biochemistry values. TABLE III Hematologic Values in Retired Greyhounds (n = 10) on Day 90

DEHYDRATION ■ SERUM CONCENTRATIONS ■ HEMOGLOBULIN CONCENTRATIONS

Compendium March 2000

Small Animal/Exotics

Creatinine is the product of platelet count (i.e., bipotential Leukocytes nonenzymatic conversion of stem cells give rise to either Mean platelet volume creatine, a muscle energymegakaryocytes or erythrocyte Platelets storage component, and is inprecursors and are subject to Erythrocyte distribution width fluenced by muscle mass. 7 hormonal stimulation for proMean corpuscular hemoglobin concentration Greyhounds have higher lean duction of one cell line over Mean corpuscular hemoglobin muscle mass than do mongrel the other). Mean corpuscular volume dogs, which probably conThe reference values obHematocrit tributes to higher creatinine tained using instrumentation Hemoglobin concentrations. at Auburn University are not Erythrocytes Sodium was elevated in alnecessarily identical to data –40 –30 –20 –10 0 10 20 30 40 50 60 most all of the greyhounds in generated at other laboratoour study. Lassen and associ- Figure 1—Percentage of retired greyhounds (n = 50) with ries using either the same or ates 2 reported a mean serum hematologic values outside the standard reference range different instrumentation. Insodium of 154 mEq/L during for Auburn University College of Veterinary Medicine. dividual laboratories must esracing season and observed that Negative values on the X-axis indicate values below the tablish their own specific refhigh sodium concentrations reference range; positive values indicate values above the erence ranges for greyhounds. have occasionally been observed reference range. However, as discussed, some in clinically normal greyof the variations found in our hounds.2 Sodium concentragroup of greyhounds have Anion gap tions in greyhounds examined been reported previously. For Total carbon dioxide by Porter and Canaday4 also example, Porter and Canaday4 Chloride Potassium studied greyhounds retired appeared to be higher than in Sodium Total bilirubin for an unspecified period and the mongrel controls, and Globulin found relative increases in Egan8 has also noted some variAlbumin Total protein ations in different greyhound erythrocyte counts, hemogloInorganic phosphate Calcium populations. Another investigabin, sodium, chloride, biliruBlood urea nitrogen tor,1 however, found no differbin, hematocrit, and aspartate Glucose Creatinine ence in sodium between the aminotransferase activity as Creatine kinase Serum alkaline phosphatase general dog population and well as relative decreases in Alanine transaminase racing greyhounds. leukocyte counts, total pro–100 –80 –60 –40 –20 0 20 40 60 80 100 Greyhounds also had intein concentrations, and eosincreased total carbon dioxide Figure 2—Percentage of retired greyhounds (n = 50) with ophil percentage. concentrations, a finding that serum biochemistry values outside the standard reference The results of the study is usually indicative of meta- range for Auburn University College of Veterinary Medi- discussed in this article sugcine. Negative values on the X-axis indicate values below bolic alkalosis. However, no the reference range; positive values indicate values above gest that reference ranges should dogs had any pathophysiolog- the reference range. be modified for retired greyic reason (e.g., vomiting) to hounds. Lack of knowledge be alkalotic. Blood-gas analyof such breed-specific variasis was not performed in any dog but could be investitions could lead to incorrect diagnosis of disease progated further to assess the acid–base status. Serum total cesses in healthy greyhounds. carbon dioxide can be altered by underfilling blood colACKNOWLEDGMENTS lection tubes, but this would result in a decrease, not an The authors thank Dr. Robert Gillette for his helpful increase, in total carbon dioxide.9 Globulin was lower in our dogs. Sullivan and coworkdiscussion and the staff of the Auburn University Cliniers5 noted a lower total plasma protein concentration in cal Pathology Laboratory for their technical help. Study the greyhounds in their study but were unable to identifunded by the Bayer Corporation, Merriam, Kansas. fy a reason.5 They did not measure albumin and globuREFERENCES lin concentrations. Those authors5 were the first to re1. Herron MR: Clinical pathology of the racing greyhound. port lower platelet concentrations in greyhounds, which Unpublished data, Texas A&M University, College Station, 5 the present study also found. Sullivan and coworkers TX. suggested that the stem-cell competition model of 2. Lassen ED, Craig AM, Blythe LL: Effects of racing on hematologic and serum biochemical values in Greyhounds. hematopoiesis was a possible explanation for the low CREATININE ■ TOTAL CARBON DIOXIDE ■ GLOBULIN ■ TOTAL PLASMA PROTEIN

Small Animal/Exotics

Compendium March 2000

JAVMA 188:1299–1303, 1986. 3. Heneghan T: Haematological and biochemical variables in the greyhound. Vet Sci Commun 1:277–284, 1977. 4. Porter JA, Canaday WR: Hematologic values in mongrel and greyhound dogs being screened for research use. JAVMA 159:1603–1606, 1971. 5. Sullivan PS, Evans HL, McDonald TP: Platelet concentration and hemoglobin function in Greyhounds. JAVMA 205:838–841, 1994. 6. Novinger MS, Sullivan PS, McDonald TP: Determination of the life span of erythrocytes from Greyhounds, using an in vitro biotinylation technique. Am J Vet Res 57:739–742, 1996. 7. Duncan JR, Prasse KW, Mahaffey EA: Veterinary Laboratory Medicine. Clinical Pathology, ed 3. Ames, IA, Iowa State University Press, 1994, pp 179–180.

8. Egan PSA: An evaluation of serum electrolyte levels in the normal Greyhound. Irish Vet J 31:101–111, 1977. 9. James KM, Polzin DJ, Osborne CA, et al: Effects of sample handling on total carbon dioxide concentrations in canine and feline serum and blood. Am J Vet Res 58:343–347, 1997.

About the Authors Dr. Steiss is affiliated with the Scott-Ritchey Research Center and the Department of Small Animal Surgery and Medicine, Dr. Brewer with the Department of Small Animal Surgery and Medicine, and Drs. Welles and Wright with the Department of Pathobiology, College of Veterinary Medicine, Auburn University, Alabama.

???? ■ ???? ■ ???? ■ ????