1261 slices of buttered white bread (30g, 240 kcal for the butter and 100g, 250 kcal for the bread’) at an approximate cost of 4-5p. M.R.C. Epidemiology Unit (South Wales), 4 Richmond Road, Cardiff CF2 3AS.

CAROL A. WESTLAKE DEE A. JONES

ECTOPIC PREGNANCY AND THE I.U.C.D.

SIR,—Isupport the views expressed by Mr Weekes and Dr Sutherst (Dec. 6, p. 1144) on pelvic infection in the aetiology of ectopic pregnancy and their reservations on the conclusions of Dr Beral6 on the role of the intrauterine contraceptive device (i.u.c.D.) as given in your editorial (Nov. 15, p. 963). The diagnosis of pelvic inflammatory disease is unsatisfactory, and the numbers of cases coded as salpingitis and oophoritis in the Hospital In-patient Enquiry are suspect. Clinicians form a spectrum of opinion from those recognising definitive symptoms and signs only (missing the mild cases) to those readily applying the disgnosis to obscure symptoms and

treating some patients unnecessarily. The traditional microbiological diagnosis is

from samples taken from the endocervical canal. This is often unsatisfactory. In South Glamorgan, the isolation-rate for Neisseria gonorrhœœ in salpingitis by this means is usually 1-3%, but with strict attention to technique it has been raised to 29% .7 Some infections may be caused by mycoplasmas and chlamydix, but few hospitals have the facilities to isolate them. There is a local secretory immune system in the endocervix producing IgA.8 Failure to isolate convincing pathogens from the endocervix could be due to their elimination there by this system, while their progress in the tubes continues unchecked. Laparoscopy should be undertaken more often but is not the ultimate solution to diagnosis. It may reveal many unexpected cases of pelvic inflammatory disease and, conversely, refute many clinical diagnoses;9 but cases can still be missed. 10 Dr Beral singles out the ’Graviguard’ (copper 7) l.U.C.D. as possibly causing a greater increase in ectopic pregnancy than other coils. If the underlying cause is ascending infection, it is unlikely to be gonococcal, since the copper content of this coil is gonococcicidal.11

proviso that the actual measurements, priate units, are reported as well. As Professor with the

in the approLennox says, with modern calculators the conversion presents no problem and when, as in this hospital, the whole process is computerised, it would be little additional trouble. Our computer also knows the age and sex of our patients so that it could easily be programmed to give suitably adjusted normals when appro-

priate. To give an opportunity for a thorough discussion of the pros ,

and cons of such a system a meeting of the Section of Measurement in Medicine of the Royal Society of Medicine has been arranged for April 26, 1976, under the title Simplification of Laboratory and other Reports, and it is hoped that as many as possible of those inerested will attend. Speakers on statistics, clinical chemistry, respiratory measurements, and on the clinical point of view have already been selected, but I would welcome speakers from other disciplines and especially any who are invincibly opposed to such a scheme. It is also proposed to carry out a limited pilot trial of the scheme in this hospital. Northwick Park Hospital and Clinical Research Centre, Watford Road, Harrow, Middlesex HA1 3UJ.

DO DIETARY LECTINS PROTECT AGAINST COLONIC CANCER? are plant proteins which have the ability to the surface carbohydrates of many mammalian cells. They are thus endowed with a multitude of abilities,’ which vary from one lectin to another. Broadly, their capabilities include : (1) agglutinating erythrocytes; (2) agglutinating bac-

SIR Lectins

bind

neoplastic (and embryonic) cells in preference to the normal adult equivalents.’ This last property endows some lectins with a protective effect against experimental carcinogenesis in laboratory animals.3 Many lectins are toxic or naturally bound toxins. In

R. A. SPARKS

Cardiff CF2 1SZ.

NORMAL=10±2

SIR,—Iwas interested to read Professor Lennox’s letter (Nov. 29, p. 1085) because I have been canvassing a similar approach for some time amongst my clinical and laboratory

colleagues. Professor Lennox’s scheme has been suggested before12 and is undoubtedly the logically and statistically correct solution to the problem, but "normal=0" is a rather strange concept to many people and gives no idea of the magnitude of the range in relation to the mean. I have therefore suggested that the normal should be 10 ± the number of standard deviations, giveing a range of 8-12 or +20% which seems to be the normal range for many clinical measurements. A normal of 100, although there is the historical precedent of haemoglobin, gives a spurious air of precision to the measurement. Where appropriate, however, there is nothing to prevent reporting to 0.1 S.D.

So far the reaction from my

monotonously enthusiastic,

even

has been almost amongst clinical chemists,

colleagues

5. McCance, R. A., Widdowson, E. M. Spec. Rep. Ser. med. Res. Coun. 1969, no.297. 6. Beral, V. Br. J. Obstet. Gynæc. 1975, 82, 775. 7. Sparks, R. A., Davies, A. J. Br. J. vener. Dis. (in the press). 8. Rebello, R., Green, F. H. Y., Fox, H. Br. J. Obstet. Gynæc. 1975, 82, 812. 9. Jacobson, L., Westrom, L. Am. J. Obstet. Gynec. 1969, 105, 1088. 10. Kenney, A., Greenhalf, J. O. Br. med. J. 1974, i, 519. 11. Cohen, L., Thomas, G. Br. J. vener. Dis. 1974, 50, 364. 12. Healey, M. J. R. Ann. clin. Biochem. 1969, 6, 12.

to

teria ; (3) inducing lymphocyte transformation; (4) stimulating mast-cell degranulation;:! and (5) agglutinating and damaging

to

Cardiff Royal Infirmary, Newport Road,

B. M. WRIGHT

spite of their ready availability and wide usage as labora-

tory tools, little thought has been given to their biological role.

particular, the literature does not dwell on the obvious consideration that the mammalian alimentary tract must be exposed to many different lectins in the normal process of eating and digestion. It is, however, a commonplace observation that a meal of beans or other seeds (rich sources of lectins) increases intestinal motility as well as mucus and gas production, and it is reasonable to infer that the lectins in the food are responsible. In this way, the body is protected from their

In

toxicity.

-

We theorise that the body’s response to lectins would protect against intestinal cancer by a number of possible mechanisms: (1) mast-cell degranulation would cause inflammation and increased mucus production, thus increasing faecal bulk and tending to sweep away malignant cells and carcinogens; (2) lectins would bind to the mucosal cells,4 inducing mitosis and increasing epithelial turnover, thus allowing less opportunity for a neoplastic cell to "take"; (3) a similar process would stimulate local lymphocytes non-specifically to cause cytotoxicity ; and (4) the neoplastic cells themselves would be susceptible to direct damage by the lectin. If this theory is correct, appropriate lectins by mouth should be of use in the prophylaxis (and possibly treatment) of colonic cancer. It is worth noting in this context that diets naturally rich in vegetable fibre will also be rich in lectins.5 A similar 1. Lis, H., Sharon, N. A. Rev. Biochem. 1973, 42, 541. 2. Hook, W. A., Dougherty, S. F., Oppenheim, J. J. Infect. Immun. 1974, 9, 903. 3. Inbar, M., Ben-Bassat, H., Sachs, L. Int. J. Cancer, 1972, 9, 143. 4. Etzler, M. E., Branstrator, M. L. J. Cell Biol. 1974, 62, 329. 5. Stoddart, R. W. Personal communication. 1975.