i~ter~tio~al Jo~r~u~ of Cardiolo~, 32 (1991) 361-364 0 1991 Elsevier Science Publishers B.V. ~167-5273/91/$03.50 ADON;IS 0~67527391~194M

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CARD10 01300

Anti-str~pto~i~as~ levels in Indian patients

Thomas Alexander I, S. ~is~naswami ’ and Uma ~anduri ’

De~~rtme~t~ of ’ Cardjolo~ and 2 Clinical Pat~~~o#, C~r~tia~ medical College ~os~~ta~, Vehre, India

(Received 16 November 1990; revision accepted 26 March 1991)

Aiexander T, ~ishnaswami S, Khanduri U. ~ti-streptokinasc levels in Indian patients. Int J Cardiol 1991:32:361-364.

Levels of anti~strepto~nase anti~ies were measured in 75 Indian patients who were divided into three groups. The first group consisted of 25 healthy blood donors; the second group of 25 patients with ischaemic heart disease with stable angina; and the third group of 25 patients with acute myocardial infarction. The mean level of anti-st~pto~nase for the entire group was 0.37 SD 0.20 million interna- tional units (IU) (range 0.09 to 1.15 million IU). There was no signi~cant diffe~nce in the anti-strep- tokinase levels among the three groups. In order to neutralise the anti-strepto~nase levels in 90% of the study ~pulation, 0.57 million IU of st~pto~nase was necessary. These levels are more than twice the current Western levels. In the light of this study, it may be necessary to reconsider the adequacy of the conventional dosage of strepto~nase while treating acute infarctions in India and, possibly, other tropical countries where prevalence of prior streptococcal infection is high.

Key words: ~ti-streptokinase antibody; ~yocardial infarction; Streptokinase dosage

Introduction

Administration of streptokinase results in thrombolysis and reperfusion of the occluded coronary arteries in a high proportion of patients with evolving myocardial infarction. Previous streptococca1 infections, however, have been shown to produce antibodies that cross react with, and neutralise, streptokinase [l]. Several investi- gators have demonstrated that the antistreptoki-

Correspondence to: Dr. S. ~ishnaswami, Dept. of Cardiol- ogy, C.M.C. Hospital, Vellore 632 004, India.

nase titres in 90% of the Western population fell below 0.25 million IU [Z-4]. Current dosage schedules aHow for the neutralisation of these antibodies by a portion of the streptokinase ad- ministered, while leaving most of the streptoki- nase free to form complexes with plasminogen and initiate thromboIysis.

Streptococcal infections in the community are common in India [S], and probably also in other tropical countries. This would result in higher antistreptokinase titres in the general population which, in turn, would necessitate a higher dose of streptokinase for thrombolysis. The present sur- vey was done prospectively to investigate levels of

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antistreptokinase in Indian patients and to com- pare them with published data in the Western population.

Patients and Methods

Patient selection

Blood was collected from 75 persons who were divided into three groups. The first group in- cluded 25 healthy blood donors aged between 40-60 years (mean 49.2, SD 5.8). The second group comprised 25 patients with ischaemic heart disease and stable angina. Their ages ranged from 42 to 68 years with a mean of 55.4, SD 6.9. These patients with on nitrates, betablockers and/or calcium channel blocking drugs. Twenty-one of the 25 patients were also on aspirin at a dose of 150-300 mg a day. The third group comprised 25 patients admitted to the coronary care unit with acute myocardial infarction. There were 18 pa- tients with anterior myocardial infarction and 7 with inferior myocardial infarction. Their ages ranged from 42 to 70 years with a mean of 56.2, SD 7.6. Of these patients, 22 arrived within 24 hours of infarction and 3 patients between 24-48 hours. There was no history of recent streptococ- cal infection in the entire study group.

luted with physiological saline to give dilutions from 100 IU/ml to 4000 IU/ml. Initial neutrali- sation was done using 5 tubes with dilutions of 400 IU/ml, 500 IU/ml, 600 IU/ml, 750 IU/ml and 900 IU/ml. If the end point was not reached with these, then the plasma was tested with fur- ther dilutions of streptokinase.

The procedure was as follows: 10 ~1 of each of the dilutions of streptokinase was mixed with 100 ~1 of the test plasma. 10 ~1 of freshly prepared bovine thrombin at a concentration of 100 units/ml was then added. Formation of a plasma clot was confirmed in all the tubes, which were then placed in a water bath at 37°C for 10 minutes. The lowest concentration of streptoki- nase that produced complete lysis of the clot at the end of 10 minutes was noted. The final con- centration of streptokinase in the tube was calcu- lated using the formula: dilution of streptokinase in tube/lo. The plasma volume was separately estimated in each patient using weight and haematocrit ratio and the total capacity to neu- tralise streptokinase was estimated by multiplying it with the streptokinase neutralisation titre [4].

Statistical analysis

Analysis of variance (ANOVA) was used to compare the mean of the three groups.

Blood collection Results

Venous blood was anticoagulated with 3.8% sodium citrate in a ratio of 1: i0 for all samples. The blood was centrifuged immediately at 1500 x

g for 5 minutes and the platelet-poor plasma was separated and stored frozen at - 70’ C till the time of analysis. Blood from patients who had suffered acute myocardial infarction was drawn immediately on arrival into the coronary care unit and prior to any infusion of streptokinase. All samples were thawed at 37 ‘C just prior to test- ing.

Table 1 shows the antistreptokinase titres ob- tained in the different groups of patients. In the first group, composed of 25 healthy blood donors, the antistreptokinase titres ranged from 0.12 to

TABLE 1

Neutralization capacity in million units

Mean SD Ranae

Estimation of anti-streptokinase titres

The following method was employed for esti- mation of the antistreptokinase levels. Streptoki- nase (Hoechst Pharmaceuticals) was freshly di-

Healthy blood donor group 0.37 0.20 0.12-0.84 Stable angina group 0.35 0.20 0.09 - 0.99 Acute myocardial infarction

group 0.37 0.20 0.09- 1.15 Entire group 0.37 0.20 0.09- 1.15

SD = standard deviation.

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

ANTI SK ANTIBODY TITRES

( in million I.“.)

Fig. 1. Cumulative percentage of patients with their corresponding antistreptokinase (SK) antibody levels.

0.84 million IU with a mean of 0.37 million IU. The second group, consisting of 25 patients with ischaemic heart disease and stable angina, had antistreptokinase levels between 0.09 to 0.99 mil- lion IU with a mean of 0.35 million IU. The third group consisting of 25 patients with myocardial infarction showed antistreptokinase levels be- tween 0.09 to 1.15 million IU with a mean of 0.37 million IU. There was no statistically significant difference among the three groups.

Taking all the patients together, the antistrep- tokinase levels ranged from 0.09 to 1.15 million IU with a mean of 0.37 SD 0.20 million IU. Fig. 1 shows the cumulative percentage of patients with their antistreptokinase levels. It can be seen that 0.57 million IU of streptokinase would be neces- sary to neutralise the antistreptokinase levels in 90% of the patients.

Discussion

In the early days of thrombolytic therapy, dosage of streptokinase was determined by a dose titration technique and tailored to the individual patient so that similar levels of clot dissolving activity could be induced in all patients. This was a time consuming process. Since then, a conven- tional dosage of 1.5 million units of streptokinase has been used, which leads to variable levels of plasma thrombolytic activity, but has immensely simplified thrombolytic therapy.

Verstraete and associates [6] reviewed 8 stud- ies done by various European and American groups prior to 1965. The mean levels of anti- streptokinase in these studies varied between 0.15 to 0.36 million IU. The mean for the total group was 0.29 million IU. In their study of 132 pa- tients, the mean level was 0.35 million IU. Subse- quent reports have, however, shown lower levels of antistreptokinase. Hirsh and associates [2] showed in 1970 that 88% of 80 patients tested had antistreptokinase titres below 0.25 million IU. Reports by James [3] in 1973 and Jalihal and Morris [4] in 1990 have shown that antistreptoki- nase levels in 90% of the population are below 0.25 million IU. Thus, there appears to have been a substantial fall in antistreptokinase titres in the Western population after the mid 1960s. This appears to parallel the dramatic fall in cases of rheumatic fever recorded since the mid sixties [7]. This could indicate lower incidence of streptococ- cal infection in the community or, more probably, less virulent attacks of infection resulting in lower production of antibodies [S].

Our results show high antistreptokinase titres, which are comparable to Western levels prevalent in the fifties and early sixties. The mean level of antistreptokinase in this study was 0.37 million II-J, with 90% of the patients having levels below 0.57 million IU. This indicates the higher inci- dence of streptococcal infection in the commu- nity.

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The higher antistreptokinase titres in Indian patients indicates that a lower amount of free streptokinase will be available to initiate throm- bolysis, and this may be inadequate. Recently, there have been some doubts expressed about the adequacy of the conventional streptokinase dosage of 1.5 million IU, even in Western popula- tions [9]. Further trials in the tropical countries are necessary to clarify if the conventional dosage of 1.5 million IU is adequate for thrombolysis or whether a higher dosage, taking into account the higher antistreptokinase titres in the population, is necessary.

Acknowledgements

We wish to acknowledge the technical heIp of Mrs. Sarala Jaipal in performing the streptoki- nase neutralisation tests; Dr. L. Jeyaseelan of the Biostatistics division for the statistical analysis; and Miss V. ~eenakshi for expert secretarial assistance.

References

1 Fletcher AP, Alkjaersig N, Sherry S. Maintenance of a sustained thrombolytic state in man. I. Induction and ef- fects. J Clin Invest 1959:38:1096-l 110.

2 Hirsh J, O’Sullivan EF, Martin M. Evaluation of a standard dosage schedule for Streptokinase. Blood 1970;35:341-349.

3 James DCO. Anti-streptokinase levels in various hospital patient groups. Postgrad Med J 1973;49(suppl):26-29.

4 Jalihal S, Morris GK. ~t~streptokinase titres after intra- venous streptokinase. Lancet 19~;335:184-185.

5 Koshi G, Benjamin V. Su~eillance of streptococcal infec- tions in children in a South Indian community: a pilot survey. Indian J Med Res 1977;66:379-388.

6 Verstraete M, Vermyten J, Amery J, Vermyten C. Throm- bolytic therapy with streptokinase using a standard dosage scheme. Br Med J 1966;1:454-456.

7 Gordis L. The virtual disappearance of rheumatic fever in the United States: lessons in the rise and fall of the disease. Circulation 1985;72:1155-1162.

8 Stetson CA. The relationship of antibody response to rheumatic fever. In: McCarty M, ed. Streptococcal infec- tions. New York: Columbia University Press, 1955,208~218.

9 Jacob Six A, Louwerenburg HW, Braams R et al. A Double blind randomised multicenter dose-ranging trial of intra- venous streptokinase in acute myocardiai infarction. Am J Cardiol 1990;65:119-123.