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As part of an international co-operative study of the International Committee for Standardisation in Haematology, human brain thromboplastins prepared by the acetone-extracted and phenol-saline extraction techniques have been compared as to the yield, the proportion of reagent discarded and wasted, and the sensitivity related to an international standard, the British Comparative Thromboplastin standard (BCT). The phenol-saline extract showed greatly improved sensitivity with greatly reduced batch-to-batch variation as compared with the acetone-dried preparation. In addition, the sensitivity of this reagent conformed to that of the BCT. The implications of the use of such a standardised reagent to the therapeutic management of oral anticoagulant therapy are: (i) standardised, reproducible results; (ii) results comparable with those carried out by other laboratories using a similarly standardised reagent; and (iii) stable therapeutic range.

Autoantibodies were solubilized from washed platelets by three successive freeze thaw cycles followed by sonication for 15 seconds at maximum intensity (MSE Mk 2). The disrupted platelets were centrifuged at 30,000g for 20 minutes and the supernatant was heated at 56°C for 30 minutes followed by centrifugation at 3,000g for 5 minutes. An aliquot of the supernatant was diluted with 0,01M phosphate buffered saline pH 7.4 to give a final concentration equivalent to about 5 × 106 platelets/ml. Fifty microlitres of the diluted extract was adsorbed onto the wells of a microtitre plate by incubation at room temperature for two hours. The wells were then washed three times with 0,01M phosphate buffered saline pH 7.4 containing 0,05% Tween (Tween-PBS) and the adsorbed antiplatelet IgG reacted with 50μl of an iodine-125 labelled affinity isolated goat antihuman (heavy chain specific) IgG, specific activity ≃ 50μCi/ μg (California Antibodies) for one hour at room temperature followed by three washes with Tween-PBS. A standard curve was constructed and run in parallel, in the dose range 0,l-100ng using purified human IgG (Miles Laboratories). The separated wells were counted in an automatic gamma spectrometer (Packard 3003) and the results calculated on a desk-top computer (Hewlet-Packard 9800) using a Rodbart weighted Logit-Log transformation (f = 0,996). A relatively poor arithmetic correlation was found between whole blood platelet counts and measured platelet bound IgG (r = -0,42), whereas a better correlation was obtained using a log-log plot (r = - 0,84).The results in ng/106 platelets were - Known ATP 133,2 ± 154, other autoimmune diseases with thrombocytopenia 212,0 ± 202, non-immune thrombocytopenia 18,6 ± 4,8, normal healthy controls 11,4 ± 3.7

An elderly woman presented with a postoperative bleeding problem, and a presumptive diagnosis of factor XIII (fibrin-stablilizing factor) deficiency was made. However, on further testing, an inhibitor to factor XIII was detected. She was on isoniazid (INH) therapy at the time. INH has been implicated in other patients who have developed inhibitors to factor XIII, and it was felt that this was the reason for this patient developing the inhibitor. The patient subsequently died from a cerebral haemorrhage, a well-described complication of factor XIII deficiency.

Since the platelets of patients with familial hypercholesterolaemia (FH) are hyperaggregable, the inhibitory effect of low-dose aspirin on platelet aggregation in response to adenosine diphosphate, collagen, adrenaline and arachidonic acid was tested in 9 young adult patients with FH and compared with that in 9 normal subjects. After a single oral dose (150 mg) of aspirin the degree of inhibition of platelet aggregation was the same in the two groups, as was the recovery time (in days) for full restoration of platelet aggregation . In a second experiment in which 162 mg aspirin was administered daily for 28 days, inhibition of platelet aggregation was sustainable in both the patient and the control groups. These results suggest that despite the recognized hyperaggregability of platelets from patients with FH, daily low-dose aspirin ingestion effectively inhibits their in vitro aggregation and may therefore prove beneficial as supplemental therapy to reduce the rate of myocardial infarction in this high-risk group.

Plasma viscosity (PV) and the erythrocyte sedimentation rate (ESR) were determined in 343 patients. The results were correlated with the presence or absence of a clinical diagnosis usually associated with a raised ESR. The percentages of false-positive results were 4,9% and 3,8% and those of false-negative results were 12,8% and 13,1% for the PV and ESR respectively. PV measurements led to the detection of 8 cases of hypoproteinaemia in patients with normal ESR values, and could also detect and quantify hyperproteinaemias. In coeliac disease the PV correlated closely with the total plasma protein measurement. In a case of subacute bacterial endocarditis (SBE) the two tests varied with the disease process in approximately parallel fashions. PV measurements have several important technical advantages over the ESR, and could replace the ESR as a primary screening test for organic disease. They can also be used to detect hypoproteinaemia in a malnourished population.

Congenital antithrombin III deficiency is a rare but well-documented abnormality. A young man presented with pulmonary embolism and was found to be suffering from this condition. His family history revealed numerous members with venous disease and its complications. Treatment of the acute episode and prophylaxis are discussed.

The change to the reporting of haematology laboratory results in the SI is now occuring in South Africa. To facilitate uniformity and standardization, the recommendations of a subcommittee of the Southern African Society for Haematology are presented.

The effect of ultra-low-dose aspirin on platelet aggregation and thromboxane B2 (TXB2) production was studied in two groups of normal subjects. Group 1 received 162 mg/d and group 2 received 20 mg/d for 4 weeks. For the first 2 weeks the effects were similar in the two groups, namely inhibition of aggregation and inhibition of TXB2 production. However, after 4 weeks there was significantly less inhibition of platelet aggregation in those receiving 20 mg/d. Inhibition of TXB2 production in the two groups was not significantly different. Two of 9 individuals receiving 20 mg/d showed an escape from the aspirin effect by the 4th week. When 40 mg/d was given to these 2 individuals they again responded. A daily dose of 20 mg aspirin is therefore too small to maintain adequate inhibition of platelet function in normal subjects.

Oral anticoagulants were introduced into clinical practice in the late 1940s. An initial wave of enthusiasm was followed by a period of scepticism in the late 1950s and 1960s. During the 1970s and recently a number of studies have revealed new evidence of clinical benefits in many thrombo-embolic conditions. The importance of correct dosage based on sound laboratory control has been recognized as a fundamental prerequisite for efficient use of this form of therapy. A reassessment of the correct therapeutic range based on prothrombin assays which conform to an international standard has resulted in more effective dosage within acceptable limits of safety. Currently accepted indications for oral anticoagulation therapy and the optimal therapeutic ranges for various thromboplastin preparations are reviewed.

Efficient anticoagulation with warfarin therapy requires optimal dosage. An international programme of standardization of prothrombin time tests has been developed in order to achieve correct dosage and efficient anticoagulation. Many South African laboratories use a more conservative therapeutic range for the prothrombin time than that recommended by international bodies. Consequently, warfarin dosage is often lower in the RSA than in many other countries. The use of a slightly lower therapeutic range in the RSA would improve anticoagulation without increasing the risk of haemorrhage. Practical guidelines for efficient warfarin therapy, including induction and maintenance dosage, therapeutic range, management of overdosage, contraindications and use during pregnancy and lactation, are discussed.

The multiracial population of the African continent provides a unique source of study in regard to environmental, genetic and epidemiological factors in the aetiology of disease in general, and is of particular interest to the cardiologist. The study of geographical pathology in the natural laboratory provided by this vast continent is of particular importance at the present time, because of the rapid development and emergence from the primitive state of the African populace. Nationalism and industrialism have, since the end of the Second World War, created a number of new states, the people of which show an increasing interest in the way of living common to the Western world.