Haematological Values in Healthy Cats

H r. vel .}. ( 1978 ), 134, 524

HAEMATOLOGICAL VALUES IN HEALTHY CATS By C. W. OSBALDISTO N

Department of Pathology, University oj South Carolina School of Medicine, Columbia, South Carolina 29208

SUMMARY

Haematological values obtained on two large groups of healthy adu lt cats kept under similar husbandry conditions are presented. One group of cats was from a specific pathogen-free cattery and the other group had been exposed to co mmon feline illnesses three to six months previously, The frequency distribution of red and white b lood cell parameters was skewed and, th erefore , results are presented as media n values together with 95% limits . The ranges for normal values are extended as compared with most other domestic animal species . White blood cell co unt was particu larly variable, ranging from 4000 to 28000 cells/l.d . The data suggested normal va lues of neutrophils and lymphocytes shou ld be expressed as percentage of total leucocyte concentration rather than in terms of abso lu te concentration. The med ian values for non-segmented neutrophils was 10% of total leucocytes a nd the ratio of segmented to band neutrophils (SI B) was 6 : 1. A third group of acute ly ill cats was studied. In that group 77% of cats had neutrophil concentrations within th e range found in normal cats, but the median percentage of band neutrophils was 25% and the SIB ratio was 1· 5 : 1. The resu lts suggested that the SIB ratio rather than the total b lood leucocyte concentration may have useful application in fe line medicine as an index to neutrophil response to tissue injury.

I NT ROD UCT IO N

In their textbooks, both Schalm, J ain & Carroll (1975 ) and Schermer (1967 ) pointed out the wide variation in normal haematological values in cats reported by various investigators. Some authors reported the haematological data in healthy cats to vary between wide limits whereas others reported limited ranges for normal values. As normal haematological values in most animal species vary within narrow limits the purpose of this study was to determine whether.cats maintained under standardized conditions have limited ranges of normal values. This paper reports the haemograms of two groups of healthy adu lt cats. Unlike other studies in which health was determined sole ly by clinical examination at the time of blood sampling, the an imals in this study were observed to be h ealthy for at least one month prior to and one month after having blood sampled. One group of cats was derived from a specific pathogen-free colony, TIlaintained in animal rooms

HAEMATOLOGICAL VAL UES I N HEALTHY CATS

525

iso lated lroll1 ot her cats and animals but with o ut husbandry proced ures to ma intain the group pathogen free. Th e second group of cats was lro m a co lo ny which had co lltact exposure with common cat disease three to six months pri o r to th e present st ud y. Another difference from previously reported studies was th a I neutrophil s were class ihed as band or segmented cells using criteria established lor huma n haematology (Orfa nkis et ai., 1970) rather than using criteria applied in veterinary haemato logy (Scha hn et ai. , 1975). The data ob ta ined from healthy ca ts was co mpared with tha t o btained from a group of acutely ill cats to tes t wh ether subcla ss ih ca tion o f ne utrophil s had potential clinical application . MATERIALS AND METHODS

T hree groups of yo ung ad ult cats were studied. The first group of 14 1 hea lth y ca ts had been raised in a specific pathogen-free ca t colony and had b een transferred to new quarters and ma intained as a separate but not pathogen-free co lony (gro up I). These cats were sero logically negative for feline leukemia virus infection. Th e second group or 19 1 ani ll1a ls were the healthy survivors of cats purchased three to six months previously froll1 dealers. After purchase they had b een quarantined lo r fo ur to Eve weeks and were then housed individually or in groups of 10 to 20 in a room (gro up 2l. All the cats in this study were observed to be healthy for at least lo ur weeks prior to being stud ied. The cats in group I were observed for four to eight weeks after being bled and had no evidence of ill health. The health status of the ca ts in group 2 was observed fo r at least four weeks and in many cases for longer than six months after being bled . The cats showed no evidence of di sease. All animals were fed Purina Cat Chow (Ralston Purina Company, St. Louis, M .) ad lib. The third group of83 a nimals (gro up 3) were cats admitted to an intensive care unit with eith er a traumatic or acute resp iratory infection . Blood samp les were obtained from these ca lS as soon as they were admitted to the unit and before any therapeutic measures had been given. One blood sample was o b tained from each animal by jugular venipuncture. In the case of group I and group 2 animals, the hair was clipped from the sk in o f the neck severa l days before the blood sample was collected. Experienced techni cians app lied minill1ull1 restraint in holding the cats during samp ling. Blood was collected into the ant icoagulant ethylene diamine tetraacetic acid ( I mg/ml b lood ) fo r all d eterminations. Red and white blood cell counts were performed with a Clay Adams Acc ustat cell counter (Becton Dickinson Co. , Cockeysville, Maryland ) which had been previo u sly calibrated for cat cells. Aliquots of blood for each count were prepared with a Unopette (Becton Dickinson so., Cockeysville, Maryland ) red cell and leucocyte dilution system. Each aliquot was counted three times and the average obtained. Platelet numbers were counted after appropriate dilution by phase microscopy. Smear preparations were made within 30 min after blood collection. Haematocrit was d etermined by a micro p roced ure. Haemoglobin concentration was d etermined by a cya nmethaemoglobin method. White blood cell differential counts were performed after sta ining with Giemsa stain. Differential counts were performed by several technologists to ensure that the res ults obtained were representative of the blood samples. Particular attention was given to differentiating segmented and band forms of neutrophils . The convention

BRITISH VETERINARY JO URNAL , 134 , 6

526

established in the 1949 report of the Committee for Clarificatio n o f the No menclature of Cell s a nd Diseases of the Blood and Blood-forming Organ s (Alt et ai., 1949) was used . A band cell was defined as any cell of the granulocytic seri es which had a nucleus that co uld be described as a curved or coiled band, no matter how ma rked the indentati o n, if it did no t comp letel y segment the nucleus into lobes co nnected b y a filament. A segm ented cell was d efined as any polymorphonuclear cell in which the lobes o f the nucleus were connected by a filament. Res ults were a nalysed using standard statistical procedures (Sned ecor, 1956) Frequency plo ts were made for white blood cell , neutrophil , lymph ocyte, monocyte, eosino phil and red bloo d cell co unts , haematocrit, haemoglobin concentra tio n and mean corpuscular vo lume of red cells (MCV). Appropriate stati stical procedures were a pplied depending upon wh eth er the populatio n had skewed o r normal distributio n. RESU LTS

Red cell data, normal cats Statistical data relating to red blood cells were compiled for animals in groups I and 2 {Table 0 . Only haematocrit values showed binomial distribution (Fig. J) The frequency distributions of red blood cell counts and haemoglobin concentrations were skewed slightly toward the higher end of their respective ranges. Because of this, the mean and 95% limits of the populations rather than the standa rd devia tion derived fro m the data are shown (Table I) . The animals in group I had greater m ean values for haematocrit, red blood cell count and haemoglobin concentration than tho se in group 2. Comparison of the population ranges showed that group 2 animals had T ABL E I E RY T HRO CYTE V AL U ES I N H EALT HY CATS

No . cats

White cell concentration cells/ill

PCV

Hb

RBCx 10 6

M CV

MCH

mIIdl

g/ dl

cellS/ill

jl

pg

MCH C g/dl

Group 1 44 38 52

5000-10000 10- 15 000 15- 20000 > 20000 Median 95% limits

0· 32 0 ·3 6 0 ·36 0 ·3 6 0· 36 0· 25-0 ·49

10 ·5 11 ·8 12·2 11·9 11 ·9 7·4-16 ·2

7· I 8 ·2 8· 5 8 ·6 8· 3 4 ·8-10·9

45·3 43· 7 4 2·5 41· 7 42· 8 35 ·1 - 55 ·4

14· 9 14· 5 14 ·4 13·9

<5 000 5-10000 10-1 5 000 15- 20000 > 20000 Median 95% limits

0 ·29 0 ·29 0 ·29 0· 33 0·35 0 ·3 2 0 ·24-0 ·52

9 ·8 10·0 10·1 11·2 12· 0 10·8 7·3-16 ·8

6 ·3 6 ·3 6 ·2 7 ·2 7 ·6 6 ·9 4 ·8-11 ·9

46 2 46 ·2 46 ·9 46 ·0 46 ·6 46 ·4 34· 7-56 ·2

155 15 · 7 16·4 15· 6 15· 7

33

33 34

33

Group 2 9 23 54 52 53

34 34 34 34 34

HAEMATOLOGICAL VALUES IN H EALTHY CATS

527

Group I

Hoematocrit %

FiK. I. Frequency d istributi on o fhaemato crit values in two groups o rhealth y cats .

extended lower values for each d ete rmination. Because of this freq uency di stributio n ofMCV was markedly skewed in group 2 cats but not in group I (Fig. 2). Beca use of the tendency towards skewed distributio ns in some parameters, the data was divided into subpopulations . No sex differences were found. Subgrouping o n the basis of total white blood cell co unts showed: (a) in group I cats , there was a tendency for red cell volume to decrease and red blood cell count to increase as numbers o f white blood cells increased , and (b) in group 2 cats, haematocrit and red blood cell co unt te nded to increase as the white blood cell count increased (Table I). Neither of these trends was statistically significant. Leucocyte data, normal cats The frequency distribution of segmented and band n eutrophil concentra tio ns for both groups of animals is shown in Figs 3 and 4. In contrast to the comp arative normal distribution for neutrophil counts, lymphocyte and eos inophil counts showed co nsiderable skewness towards the higher cell counts (Figs 5 and 6). The m edian and 95% limits for absolute concentration (cells/ill) of several blood leucocyte types' are shown for animals in groups I and 2 (Table II). The upper 95% limits were similar in both gro ups for all leucocyte types. The cats in group 2 had extended lower limits for white blood cell and neutrophil concentration. Twelve per cent of cats in group 2 had white blood cell co unts less than the lower limits observed for group I cats and 8% had

528

BRITISH VETE RI NARY JOURNAL, 134,6 Group I

10

'if. c: .Q

:;

.0

' ':

0

56

'" ii >u

c:

'"cr"

Group 2 18

'"

~

MCV II Fi~ . ~.

Frequency distribution or mean corpusc ular volume (MeV) in twO groups of" hea lth y calS.

lower total neutrophi l concentrations. No sex differences in abso lu te leucocyte numbers were observed. Becau se of the skewed distribution of lymphocyte and eosinophi l numbers, the data were subgrouped on the basis of total white blood cell count and analysed to establish whether the distribution of blood leucocyte types varied within the subgroups (Table II I). The correlation coefficient for abso lute TABLE II LE UC OCYTE CONCENT RATIO NS IN H EALTH Y CATS

Croup 1 (J 41 cats) Median Total leucocytesild Segmented neutrophils/~l

Band neutrophils/~ l

Lympho cytes/~ l Eos in oph ils/~ l Mon ocy tes/~l

95% limits

Croup 2 (191 cats) Median

95% limits

18000

8000-28000

15400

4000-28000

10500

3200- 16500

8400

1500- 12500

1500

800- 5500

I 700

500- 8500

4400 111 0 380

400-11000 80- 2200 80-1650

4100 970 450

600-11000 40- 2200 40-1000

529

HAEMATOLOGICAL VAL UES I N HEALTHY CATS Group I

18

12

"t-

O

c .S' 0; .D

.;:

Group

;;;

"

2

24

>u

cQ)

"

~ Q)

Lt

Ne utrophil s (cells/I" I) F i~ .

3. FreLJuency distribution of segmented ne utrophil s (celis/III ) in two groups of hea lthy cats.

TABLE iii DiFF E RENT iAL DiSTRiB UTiON OF LEUC O CYTES iN H EA LTHY CATS

Group 1 Subgroup LeucocyleJ x 103 /JJ.l

Segmented ne utrophils/ JJ.I Band n e utroph ils/JJ.I Lymph ocytes/JJ.I Eos inop hils/ JJ. I M o noeytes/JJ.l No.or eats

Group 2

> 20

5-10

10-15

15-20

4650

8500

10500 17000

<5

5-10

10-1 5 15-20

1950

4600

7000

> 20

10 500 15500

450

900

1400

2200

300

600

1000

7800

2 600

2 900 800 150 7

3700 900 300 44

4300 1 300 300 38

5 700 1200 500 52

2050 300 50 9

5500 650 150 23

3500 1000 250 54

4 300 1 500 300 52

5 600 1500 450 53

530

BRITISH VETERINARY JO URNAL, 134,6 Group I

c

30

.g

"

.0

~ 24

Group 2

U >.

u

c

Q)

"

cQ) ~

Band neut rophils (ee Ils/f Ll )

Fig. 4. Freque ncy distributio n of band neutrophils (cell/Ill ) in two groups of hea lth y cats.

neutrophil and lymphocyte concentrations in groups 1 and 2 was + 0·45 (P> 0 ·05, d.f. 3 21 ). In contrast, the differential distribution ofneutrophils and lymphocytes showed an inverse relationship; the correlation coefficient was -0·54 (P> 0·05, d .f. 321) . The relative distribution of eosinophils and monocytes was independent of leucocyte concentration. Although the relative distribution of neutrophils was influenced by total leucocyte count, the mean ratio of segmented to band neutrophils (SIB ) remained constant, i.e. there was no 'shift to the left' as neutrophil concentration increased (Table III). The median value for the SIB ratio was 6 : 1 and the range was 80 : 1 to 1· 1 : 1.

H aematological data, acutely ill cats The haematological data for the acutely ill cats with high fever (group 3) are summarized in Table IV. Comparison of the data in Tables I and IV showed the acutely ill cats had similar values for red blood cell parameters. Comparisons of the data in Table II and IV showed differences in white blood cell concentrations. As

HAEMATOLOGICAL VALUES IN HEALTHY CATS

53 1

Group I

"'

Group 2

"0

~ c:

20

'"::>

~

~

u..

16

4 Lymphocytes (celis/IL t) F i~ . S.

Frequ ency distribution of lymphocytes (cells(lll) in two groups ofhea llh y cals. TABLE IV HA EMATO LOGICAL DATA OF ACUTELY ILL CATS

Totalleucocytes

PCV Hb g/d l RBC/Ill X 10 6 MCV fI MCHCg/d l Le ucocytes/Ill Segmented neutrophi ls/ Il l Band ne utro phi ls/Il l Lymphocytes/ill Eos inophils/Ill M9 nocytes/lll No. of cats

X lOS/ill

/0

10-20

20

0·30 10 · 1 7.0 44.2 14·4 8 150

0·32 10·2 7. 1 45 · 1 14·2 16800

0 ·33 10 ·2 7.4 44· 7 13·9 30 100

3200

5600

12200

1800

4500

7800

2400 600 150 13

5400 1000 250 15

9700 1100 300 55

532

BRITISH VETERINARY JO URNAL , 134, 6 Group I

c

.~

"

.n

.~

Group 2

'6

Eosinophils (cells /jLl)

Fig. 6. Frequency dislribution o r eosinoph il s k e llS/ill ) in two groups of hea lthy cal s.

compared with the data for healthy cats, the acutely ill animals had (a) extended upper limits for total leucocyte concentrations, 23% of sick ca ts having leucocyte concentrations exceeding the upper limits of the normal values, (b ) marked decrease in relative distribution of lymphocytes as leucocyte concentration increased, and (c) a marked decrease in SIB ratio. The frequency distribution of SIB ratio for hea lthy and acutely ill cats is shown in Fig. 7. The median ratio for healthy cats was 6 : 1 and sick cats was 1·5: 1. Analysing the data on the basis of normal distribution, the SIB ratio for the two populations was significantly different (P> 0·05, d.f. 414 ). Platelet data, normal cats Platelet counts were performed on all cats in group 1. The distribution of platelet concentration skewed towards the greater concentrations. The med ian value was 30 000 platelets/~l, and the range was 112 000 to 780 000 platel e ts/~l. If a normal distribution was assumed, the mean and standard deviation were 330 000 ± 142 000 platelets/~l respectively.

HAEMATOLOGICAL VALUES I N H EALTHY CATS

533

Group I

25

;t. c:

.2

:;

15

.Cl

on "0

>u

10

c:



::>

0-



c::

Group 2

25

20 c .Q

"'j

~ 15 v; '0 >u

c

~I O

c::'" 5

SI B rat io Fi ~.

7. Frequency d istribution of segmented to band (S/ B) neutroph il ra lio in twO gro ups of hea lth y cats.

DISC U SSIO

Penny, Carlisle & Davidson (I970) reported that feline red bl ood cell volume was inAuenced by concentration of EDTA used as the anticoagulant. In their studies, the MCV for 128 cats was 56±6A. In another large series of cats, Schalm et al. (1975 ) reported MCV of 45 A with a range of 39 to 55 A. In the present stud y, m edian and range for MCV for cats in groups I and 2 were 42·8, 35 · 1 to 55 ·4 A and 46·4, 34· 7 to 56·2 A respectively (Table II) . The lower range for MCV was below that reported by Schalm et at. (I 975) and Penny et at. (I9 70 ). Red blood cell counts and haemoglobin concentrations in the group I cats were

534

BRITISH VETERINARY JO URNAL, 134,6

greater than similar values for goup 2 cats, whereas PCVs were similar. The mean values for each parameter were similar to published values in the literature but the ranges obtained were greater which may have been due to the larger number of cats in the study. No other paper has reported on the skewed distribution of red blood cell a nd haemoglobin values. The arbitrary subdivision of erythrocyte values on the basis of' white blood cell count showed that cats in both groups with the lowest white cell concentration had lower mean PCV, haemoglobin and red cell concentration, but had simi lar MCHC and MCH . With group 2 animals, MCV was similar in each white blood cell subdivision, but in group I animals, MCV showed an apparent inverse relationship with white blood cell concentrations. Because red blood cell and white blood cell concentrations are independently controlled, the finding of apparent interrelationship is without physiological significance. However, it does emphasize that normal erythrocyte values based on less than 50 cats could give misleading values. Schermer (967), Penny et al. (970) and Scharm et al (975 ), have studied large series of adult cats and reported red cell counts of 7·5, 6·45 and 8·5 cellS/ILl respectively. Reviews of normal feline haematology have shown the wide variation in va lues for red blood cell counts, but many authors did not state the methods by which the cells were co unted . Because cats have small red blood cells, they are not well suited for co unting by some electronic instruments. The small cell size may be below the size threshold for the instrument with the result that the count would be less than that obtained by manual procedures. Therefore, in calibrating the instrument used in this study, the lower threshold was adjusted so that small red cells would be counted and the background noise of the electronic counter would be acceptably low. In calibrating the instrument, comparisons were made with red blood cell counts obtained using a haemocytometer. Although the normal cats in this study came from two distinct subpopulations of animals, all were observed to be healthy for at least one month prior to and one month after being bled, all were used to being handled by experienced technicians and all were fed the same diet. The population differences in red blood cell and haemoglobin values were probably not related to the previous factors. The only major difference between the groups was their source; group I cats were from a feline specific pathogen-free colony and group 2 cats were laboratory-conditioned animals. However, as both groups had received similar husbandry for at least two months, the effect of previous husbandry would have been minor. It seems most likely that the clinical history of the groups was responsible for the observed differences . Wide variations in normal values for total leucocyte numbers have been reported in the literature. The results in this study are similar to those reported by Gilmore, Gilmore & Jones (1964). Nine cats in a total of 332 cats had total leucocyte counts of less than 5000 ceil/ILl. This observation of low numbers of leucocytes in healthy cats has been previously reported (Gilmore ~t at., 1964; Penny et aI., 1970; Schalm et aI., 1975). The upper limit ofleucocyte concentration was 28 OOOcells/1L1which was similar to values reported by Gilmore et aI. (1964) and Schermer (967). Several other studies reported the upper limits of leucocyte concentration of approximately 20000 celiS/ILl, Schalm et aI., (975) state the upper limit of leucocyte concentration in healthy cats to be 56300 celiS/ILl. The wide variation in leucocyte concentration in healthy cats suggested that this parameter would be a poor index of response to infection. For this

HAEMATOLOGICAL VALUES IN HEALTHY CATS

535

reaso n, a third group of acutely ill cats was studied to es tablish whether leucocyte distribution in these cats differed from that in health y cats. The data in Table III showed that the differential distribution of neutrophils and lymphocytes was influenced by total leucocyte concentration. As total white blood cell concentration increased, the differential distribution of neutrophils increased and that of lymphocytes decreased (r=-0 ·54, d.f. 32 I). Analys is of the data in terms of relative distribution of neutrophils showed that the 95% limits were 30% and 90% irresp ective of white blood cell concentration. Similar analysis for lymphocytes showed the 95% limits were 10% and 50%. Therefore, the data suggested that with the normal feline haelllogram, the relative distribution of neutrophils and lym phocytes was a more valuable statistic for interpretative purposes than the absolute concentration of cells . Although this approach to interpretive haematology is not in keeping with obsel-vations in other species (Wintrobe, et ai., 1974 ; Schalm et ai., 1975 ), no other approach to the data proved as useful. Anderson, Wilson & Hay (1971) pointed out that there was marked individual variation in absolute lymphocyte numbers in the cal. Th e range of absolute lymphocyte concentrations in that study was 2800 to II 100 cells/ill and the range of relative distribution was 5 to 58%. In the present study, 39% of ca ts had less than 2800 lymphocytes/ill but the relative distribution was similar. The lower absolute numbers oflymphocytes in this study could not be attributed to lymphoid depletion in response to silent feline leukemia virus infection because group I cats were serologically nega tive for this virus. Feline leukemia viral antigen status of group 2 cats was not established and presumably many animals would have been positive. However, there was no difference in lymphocyte concentrations or relative distributions between the groups. Using these criteria established for human neutrophil classification (Alt et ai., 1949 ) normal cat peripheral blood contains a much greater number of band neutrophils than is found in human blood (Fig. 3). Band neutrophil concentration in blood of kittens has been reported to be 25% of total leucocyte concentration (Anderson et ai., 197 I ). I n dogs, Marsh et ai. (196 7) demonstrated the change in blood SIB ratio was a much more sensitive index of severity of infection than the blood granulocyte concentration and that it correlated significantly with fever index. In the present study, neutrophils were classified using the above criteria. The results obtained in the healthy cats in groups 1 and 2 were compared with data from the group of acutely ill untreated animals (Tables III, V and Fig. 6). The results suggested that the SIB ratio may have useful application in feline medicine, particularly as total neutrophil lymphocyte concentrations have marked individual variation.

REFERENCES

ALT, L. et al. ( 1949). Am.}. din . Path. 18,443. ANDERSON , L. , WILSON, R. & HAY, D. (197 I). Res. vet. Sci. 12,579. GILMORE, C. E., GILMORE, V. H. &]ONES,j. c. (1964). Path. Vet. 1,18. MARSH,]. C., BO GGS, D. R., CARTWRIGHT, G . E. & WINTROBE, M. M. (1967 ).]. din. Invest. 46, 1943. ORFANAKIS, N. G., OSTLUND , R. E., BISHOP, C. R. & ATHENS ,]' W. (1970 ). Am.). din. Path. 53,

647.

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BRITISH VETERINARY JOURNAL , 134,6

PENNY, R. H. C., CARLISLE, C. H . & DAVIDSON, H . A.(J970). Br. vet.}. 126,459. SCHALM , O. W. , JAI N, N. C. & CARROLL, E. J. (1975 ). In Vet erinary Hematology, p. 109. Philadelphia : Lea and Febiger. SCHERMER, S. (1967). In The Blood Morphology oj LaboraJ.ory Animals, p . 101. Philadelphia: F. A. Davis Company. SNEDECOR, C. W. (1956 ). In Statistical Methods, p . 66. Ames, Iowa: The Iowa Slate Un ivers ity Press . WINTROBE, M. M., L EE, C. R., BOGGS, D. R., BITHELL, T. c. , ATHENS,j . W. & FOERSTER,j . ( 1974). In Clinical Hematology. Philadelphia: Lea and Febiger.

(Accepted for publication 22 February 1978)