Antiphospholipid antibodies and recurrent thrombo-occlusive events

117

satisfactory serological technique since at present PCR technology available in most clinical laboratories. HCV has eluded serological detection for more than a decade and probably will continue to be elusive and to produce conflicting results. is

not

Departments of Microbiology and Paediatrics,

Hospital Ramon Y Cajal, Madrid 28034, Spain

M. MATEOS S. BALLESTERO A. M. POLANCO C. CAMARERO

M, Martos I, Moreno R, et al. Immunoblot assay as diagnostic test for hepatitis C virus infection. J Hepatol 1992; 14: 411-12. 2. Leon A, Canton R, Elia M, et al. Second generation RIBA to confirm diagnosis of HCV infection. Lancet 1991; 337: 912. 1. Mateos

RIBA-2 band intensity and PCR in HCV infection SIR,-Dr Irving and colleagues (June 6, p 1425) show that the absence of c33c or c22-3 band in donors confirmed positive for hepatitis C virus (HCV) antibodies by second generation recombinant immunoblot assay (RIBA-2, Chiron) was significantly more likely to be associated with negative PCR. They suggest that this was due either to a less virulent HCV strain with a different 5’ non-coding region (NCR) or to host factors that help in the elimination of virus replication. They excluded RIBA-2 indetenninate samples from their analysis. A significant proportion of these, in particular those with only c22-3 band, have proved viraemic by PCR.1 We feel that by excluding this group, important information is lost. RELATION BETWEEN RIBA-2 BAND INTENSITY AND PCR FINDINGS

*Number of -

samples

with each band

tFisher’s exact test

+ve=poSltlve,

ve=negaUve.

We have done nested PCR with the same 5’ NCR primers2 on 27 samples, 15 of which were RIBA-2 reactive (two bands or more) and 12 were indeterminate (one band only). The intensity of each band was rated according to the manufacturer’s recommendation from 1 + to 4 + before PCR. The table shows the relation between band intensity and PCR findings. A c22-3 band with intensity of 3+ or above was significantly more likely to be PCR positive. No significant associations were seen with the other bands. Of the 12 indeterminate samples, 8 were c22-3 only. 5 of these were 3 + or above and all were PCR positive, whereas none of the 2 + or less samples were PCR positive. These results suggest that the intensity of the c22-3 band could be used as a guide to viraemic status. We believe that it is still essential to do PCR on all indeterminate cases, but a single and strong c22-3 band should prompt more thorough

investigations and follow-up. that

indeterminate by RIBA-2 but

negative by

PCR could be false-positives in RIBA-2. However,

one cannot

Samples

were

exclude the possibility of virus variants or host factors as Irving and colleagues suggest. On the other hand, samples reactive in RIBA-2 with two or more bands but negative by PCR might be serological

false-positives. Newcastle Public Health Laboratory, Newcastle General Hospital, Newcastle upon Tyne NE4 6BE, UK

C. Y. W. TONG A. A. CODD

Chan S-W, Simmonds P, McOmish F, et al. Serological responses to infection with three different types of hepatitis C virus. Lancet 1991; 338: 1391. 2. Garson JA, Ring CJA, Tuke PW. Improvement of HCV genome detection with "short" PCR products. Lancet 1991; 338: 1466-67. 1

Antiphospholipid antibodies and

recurrent

thrombo-occlusive events SIR,-Dr Sletnes and colleagues (Feb 22, p 451) report a lack of association of IgG or IgM antiphospholipid antibodies (aPL) with increased risk of mortality, reinfarction, or non-haemorrhagic stroke in patients surviving myocardial infarction. However, several methodological concerns should temper their conclusions. The study was not specifically designed to investigate the relation of aPL and recurrent thrombo-occlusive disease. The patients were drawn from the placebo group of a treatment trial to evaluate the efficacy of warfarin after myocardial infarction. Patients were 75 years old or younger, should not have a risk of bleeding, and, most importantly, were excluded if they were thought to require anticoagulation, have atrial fibrillation, valvular heart disease, atrial embolism, and venous thrombosis. Because of this, the patients with true aPL syndrome1 were likely to be excluded from the study. By excluding patients with many features of aPL syndrome, especially other thrombotic events and valvular heart disease, Sletnes et al have, unfortunately, biased their study towards a negative result. In negative studies, it is always important to know the power of the study to detect a clinically important difference. We suspect that this study had only limited power to detect a two-fold increase in stroke risk among the myocardial infarction survivors who had anticardiolipin antibodies. High aPL values, specifically anticardiolipin antibodies, have been shown to be an independent risk factor for first ischaemic stroke in a case-control study.2 They are also associated with a high risk for recurrent cerebral ischaemic events in patients presenting with focal brain ischaemia.3 Perhaps anticephalin antibodies, as a measure of aPL, are not a good marker for recurrent thromboocclusive disease. It is also possible, in the presence of aPL, that there is a greater risk for recurrent ischaemic events after cerebral ischaemia than after myocardial infarction. The jury is still out on aPL as a prognostic marker. Center for Stroke Research, Department of Neurology, Henry Ford Hospital and Health Science Center, Detroit, Michigan 48202, USA

STEVEN R. LEVINE

Department of Medicine (Neurology), University of Texas Health Science Center, San Antonio, Texas

ROBIN L. BREY

Department of Neurology and Epidemiology, University of Maryland, Baltimore, Maryland

STEVEN J. KITTNER

1. Hams EN. Antiphospholipid antibodies. Br J Haematol 1990; 74: 1-9. 2. Antiphospholipid Antibodies in Stroke Study Group (APASS). The association of anticardiolipin antibodies with first ischemic stroke: a multi-center case-control study. Stroke 1992; 23: 161. 3. Levine SR, Brey RL, Joseph CLM, Havstad S. Risk of recurrent thromboembolic events in patients with focal cerebral ischemia and antiphospholipid antibodies. Stroke 1992; 23 (suppl I): 129-132.

** This letter has been shown to Dr Sletnes and colleagues, whose reply follows.-ED. L. SiR,—The objective of our cohort study was to find whether antiphospholipid antibodies (aPL) detected as anticephalin (aCEPHA) and anticardiolipin (aCL) antibodies, were independent risk factors for subsequent mortality, recurrent myocardial infarction, or non-haemorrhagic stroke in an unselected group of patients who had survived an acute myocardial infarction (AMI). The patient cohort studied was the placebo group of the Warfarin Re-Infarction Study. Patients were recruited from five hospitals serving the Oslo area. The decision to register a patient in the study was left to physicians working in these hospitals during the inclusion period. 1918 patients of both sexes who were 75 years of age or younger at the time of discharge from hospital were potentially eligible. Of these, 270 were excluded because they refused to participate. Total mortality in this group was higher than in the placebo group (ie, our study cohort), but the rate of cardiovascular events was lower.2 15 were excluded because of malignant disease, 16 because they died before randomisation, and 65 because they had a permanent residence outside the study area or were physically or mentally unable to comply with the study regimen. 182 were

118

excluded because of factors contraindicating anticoagulant therapy (a history of haemorrhagic diathesis or peptic ulcer disease, or, in a few cases, strong belief in the prophylactic value of aspirin). 156 patients were excluded because the referring physicians thought they required antiooagulant therapy, and this group is, of course, of particular importance in this context. We have gone through the records of all these patients: 101 were given warfarin because the physicians at one of the hospitals believed in the prophylactic value of warfarin after anterior wall myocardial infarction (n = 32) or after streptokinase therapy for myocardial infarction (n 69); other reasons were atrial fibrillation (n = 30), arterial embolism (n = 8), venous thrombosis (n = 6), valvular heart disease (n=4), and miscellaneous (n=7). The male/female ratio was 3-9 to 1 in these excluded patients and 3to 1 in our study group; the mean age was 615and 616, respectively. Of the patients excluded because of anticoagulant therapy, none had a known aPL syndrome.3 Thus, no patient populations at high risk for the end points were excluded. One might argue that the patients with anterior wall infarction and atrial fibrillation were at high risk for cerebral embolism; however, involvement of aPL in the pathogenesis of this condition is not suspected. Of the 1214 patients remaining after the exclusions, 607 were randomised to placebo and constitute our cohort. Our belief that no high-risk population has been removed is borne out by the high mortality (19-9%) and occurrence of reinfarction (20-1%) and cerebrovascular disease (7-4%) during the study period. We had measured aCEPHA and aCL in the entire cohort of 1200 patients. There was no effect of the antibodies on the end points in the warfarin group-as we found for the placebo group. Thus, the patient population studied was an unselected group of patients who had survived an AMI. Of course, our results do not exclude the possibility that high aPL values might be an independent risk factor for thrombo-embolic events in patients with other disorders--eg, patients with the aPL syndromethe existence of which we do not doubt. =

Haematological Research Laboratory, Department of Internal Medicine, Ullevål University Hospital, N 0407 Oslo, Norway

K. E. SLETNES P. SMITH M. ABDELNOOR H. ARNESEN F. WISLØFF

1. Smith

P, Amesen H, Holme I. The effect of warfarin on mortality and reinfarction after myocardial infarction. N Engl J Med 1990; 323: 147-52. 2. Smith P, Arnesen H. Mortality in non-consenters in a post-myocardial infarction trial. J Intern Med 1990; 228: 253-56. 3. Harris EN. Antiphospholipid antibodies. Br J Haematol 1990; 74: 1-9.

readily auto-oxidise, generating free radicals and other compounds that disrupt cellular function and damage cell membranes. Increased intake of highly polyunsaturated fats increases the nutritional requirement for vitamin E, but by how and

much is not known. Contamination with toxic residues is also a concern. Lead and mercury in the commonly occurring methylated form are lipophilic, as are organochlorides such as DDT, and preferentially accumulate in the lipid stores of fish living in contaminated waters. These difficulties are surmountable by careful control of production conditions. Oxidation can be kept to a minimum by refrigeration, addition of anti-oxidants such as vitamin E, and the use of packaging that excludes light and air; and toxic residues are largely removed by efficient processing. However, such manoeuvres and the stringent quality control needed to ensure consumer safety add considerably to the cost of the final product. An alternative approach might be to encourage regular fish consumption in pregnant women. As Olsen et al point out, the differences between those who received and did not receive fish oil supplements were considerably reduced when individuals who habitually ate a lot of fish were compared, suggesting that the effect of fish oil on gestation length and birthweight has a limit. In the Aarhus study seven out of ten of the fish oil group had belching; unpleasant taste and nausea were also common. Despite these effects, compliance rates of 75% were achieved, which bespeaks participant motivation and researcher persuasiveness unlikely to be found outside the context of a clinical trial. Consuming fish rather than fish oil capsules might have the added benefit of displacing other saturated and n-6 fats from the diet. Since the effects of n-3 fatty acids are much affected by the total amount and proportions of other dietary fats, this might further potentiate their effects, leading to a reduction in the amount needed. Fred Hutchinson Cancer Research Center, Gastroenterology/Hepatology Section SC-111, Seattle, WA 98104, USA

ANNE TOBIN

Neuringer M, Connor WE. n-3 fatty adds in the brain and retina: evidence for their essentiality. Nutr Rev 1986; 44: 285-94. 2. Neuringer M, Connor WE, Lin DS, Baistad L, Luck F. Biochemical and functional effects of prenatal and postnatal n-3 fatty acid deficiency on retina and brain in rhesus monkeys. Proc Natl Acad Sci USA 1986; 83: 4021-25. 3. Thomgren M, Gustafson A. Effects of 11 week increase in dietary eicosapentaonoic acid on bleeding time, lipids and platelet aggregation. Lancet 1981; ii: 1190-93. 4. Goodnight SH, Harris WS, Connor WE. The effects of dietary w-3 fatty acids on platelet composition and function in man: a prospective study. Blood 1981; 58: 1.

880-85. 5.

Thomgren M, Shafi S, Born GVR Delay in primary haemostasis produced by a fish diet without change in local thromboxane A2 production. Br J Haematol 1984; 58: 567-78.

Fish oil

supplementation

in pregnancy

Medical audit of the investigation of toxoplasmosis associated with pregnancy

SIR,-Dr Olsen and colleagues (April 25, p 1003) report evidence that

dietary fish oil supplements prolong gestation and increase birthweight. The fetus may benefit from maternal supplementation in other ways; the n-3 fatty acids abundant in fish oil are major components of neuronal and retinal tissue and may be involved in learning and visual acuity. 1;z.Studies of rhesus monkeys suggest that a supply of these fatty acids is especially important in the last trimester and first three months of life when membranes high in n-3 3 fatty acids are being formed? Several studies have examined the effect of large doses of fish or fish oil on coagulation. Modest reductions in platelet count and aggregation and lengthening of mean bleeding times by up to 50%3,4 have been reported. In one study whose participants ate a diet high in fish, prolongation of bleeding time was highly variable, ranging from 2 to 93%, and persisted for three weeks after supplementation.5 It is therefore not surprising that in the group of Danish women taking fish oil there was a trend towards increased blood loss at delivery. This trend was apparent despite the group’s very low caesarean section (< 9%) and assisted delivery rates. In other obstetrical populations with higher rates of surgical

intervention, bleeding complications could be substantially higher. If these promising findings are duplicated by other studies, fish oil might be offered to large numbers of healthy pregnant women. The safety of fish oil supplements warrants consideration. By virtue of their high degree of polyunsaturation, n- 3 fatty acids are unstable

SIR,-Increased awareness of toxoplasmosis in pregnancy has led demands for serotesting and for routine screening. However, the study of toxoplasmosis associated with pregnancy may be problematic and in 141 cases, we found that 98 (70%) received non-ideal investigation.1 Thus we introduced a programme of enhanced communication between reference centre and clinician and monitored the effect on patient’s care. All cases of acute toxoplasmosis associated with pregnancy first investigated during 1990 were included. Letters were sent to all responsible clinicians when laboratory records indicated ideal investigation had not been achieved. Further details of the case were requested in a questionnaire and educational material was provided. Reminders were sent to non-responders and a quarterly analysis of the findings was given to all participants. 130 cases of acute toxoplasmosis associated with pregnancy were studied. In addition to standard laboratory results, a further 170 letters and 60 h of administrative time were devoted to these cases. 6 cases of congenital toxoplasmosis were confirmed and 50 children were shown to be free of infection. A definite diagnosis was not made in 62 cases. A further 12 pregnancies did not proceed to term (5 spontaneous abortions, 1 intrauterine death, 6 terminations). 5 products of conception showed no histological evidence of toxoplasma infection and the parasite was not isolated from fetal to