large series of proved cases. In one reference cited, 224 patients had an allergic response involving a variety of symptoms outside the gastrointestinal tract (reference 1). No organized follow-up is described that would convince one that identification of the offending food led to cure. A second reference is only an opinion expressed by a member of the audience after hearing a paper on "Colopathy" in which allergy is not even mentioned (reference 2). History of allergy is said to be important and a "victim of severe food allergy has learned through experience what his offenders are" (reference 10). Unfortunately this is not the case with most patients with irritable colon. How then can we positively identify food allergy? As Dr. RafiZadeh says, skin tests are notoriously unreliable. The awkward inefficiency of elimination diets is well illustrated by a patient such as Shaeffer's "Richard" (reference 6). Since the irritable colon syndrome is a remitting condition, how can one be sure that the elimination of certain foods is the secret to therapeutic success? The response to placebo drugs in this condition varies from 30 to 47%, so that one cannot underestimate the psychologic effect of any treatment, including diet. The provocative testing described by Lee and Millar is interesting, but we await publication of scientific reports as to its accuracy (references 8 and 9). Meanwhile, claims that it will identify the cause, and cure the irritable colon in most patients, seem premature. In summary, food allergy is an etiologic factor in an unknown, but probably small number, of patients with the irritable colon syndrome. In some of these the diagnosis is obvious, either because the patient can connect his symptoms to certain foods, or because manifestations, such as urticaria or rhinitis, occur outside the gastrointestinal tract. When food allergy is suspected, elimination and provocative reintroduction of the offending item remain the only currently practical way to make the diagnosis. More definitive diagnostic testing would be most welcome.

hesitation that for myself and a number of other CUSO physicians very little in the way of self-sacrifice has been required. Most of us have been richly rewarded in clinical experiences and in the developmental aspects of health care in the "third world"; in addition to these rewards there is the stimulation of working and living in another culture. Most of us who came overseas with CUSO did so because we wished to, and few would say that we have not received more than we have given. I heartily endorse Dr. Wallace's request for financial contributions to CUSO because I feel strongly that it does have a viable, if small, role to play in Canada's overseas relations. But please don't think in terms of selfsacrifice. For most of us there is no other place we would rather be. AJ. REID, MD

St. Martin's Hospital PA Malindi P0 Mangochi Malawi

Contaminated vacuum tubes

To the editor: It has recently come to our attention that some of the vacuum tubes used for blood collection are contaminated with bacteria. A nonpigmented Serratia species was isolated from 3 of 13 tubes. These were from different lot numbers and contained liquid ethylenediaminetetraacetic acid as anticoagulant. They had all been prepared in Canada. Our attention was drawn to the possibility of contamination by the finding of vacuolated neutrophils on many blood films prepared from these tubes. A lesser number of tubes show bacteria in routine blood films, especially if the blood is allowed to incubate for 12 hours at room temperature. Subsequently our attention was drawn to five cases of Serratia bacteremia. The only factor common to these patients was that vacuum tubes had been used for drawing the blood; the same nonpigmented Serratia sp. was isolated from them as was isolated from the vacuum tubes. One patient had thrombophlebitis of the arm extending proximally from the venipuncture site. If one uses a technique similar to W. GRANT THOMPSON, MD, PRCP[C] Ottawa Civic Hospital that of Mendelssohn and Witts' it is Ottawa, Ont. possible to show that only a slight degree of negative pressure is sufficient cuso to draw blood from a full vacuum tube To the editor: I read with interest Dr. into a patient. This may arise during Wallace's column "One small step for a venipuncture, especially after the mankind" (Can Med Assoc J 111: tourniquet is removed. 1248, 1974) concerning Canadian phyThe solution to the problem is to sicians working with Canadian Univer- insist on sterile vacuum tubes for blood sity Service Overseas (CUSO). collection. It should not be difficult He suggests that self-sacrifice is re- for the manufacturer to provide these quired of those who serve with CUSO. since they already produce sterile vacuI cannot speak for Dr. Mellor, to um tubes. whom he refers, but I can state without These findings have been discussed 682 CMA JOURNAL/MARCH 22, 1975/VOL. 112

with the manufacturer and they have been brought to the attention of Health and Welfare Canada, where it has been confirmed that the tubes are not sterile. ..A. MCLEISH, MD

E.N. CORRIGAN, B SC, ET R.H. ELDER, MD J.C.N. wEsTwoOD, MD

Departments of laboratory medicine Ottawa General and Ottawa Civic hospitals Ottawa, Ont.

Reference 1. MENDELSSOHN K, Wsrrs U: Transmission of infection during withdrawal of blood. Br Med J 1: 625, 1945

Contraception and abortion To the editor: The comments of Dr. Kevin C. Toal (Can Med Assoc J 112: 145, 1975) deserve some dispassionate comment. Dr. Toal is entitled to his opinion. However, he should have indicated in his letter that he was speaking not as a physician but as a moralist. We are all moralists. When one attempts to practise medicine and morality simultaneously, problems arise. These problems arise not in dealing with sick people but in dealing with healthy people who bring their complex sociocultural dilemmas, of which abortion and contraception are two of current interest. Dr. Toal equates contraception and abortion. Abortion is an act that, to be carried out properly, demands medical intervention. Contraception can be carried out without the help of a physician. Abortion is "our.. problem whether we like it or not and however we choose to think about it or deal with it. Contraception is "our.. problem only if we wish it to be. As moralist, Dr. Toal states that both abortion and contraception are evil. I would recommend to him two books that deal with this. The first is "Contraception" by John T. Noonan, outlining a Christian viewpoint. The second is "Marital relations, Birth Control and Abortion in Jewish Law" by David M. Feldman. These recommendations are not designed to alter Dr. Toal's opinions on morality but to deepen them. MORTON S. RAPP, MD

Sunnybroolc Hospital Toronto, Ont.

Abnormal patency of eustachian tube from oral contraceptives To the editor: Most physicians are aware of the more common and certainly more serious side effects of oral contraceptive agents. One side effect not listed in any of the manufacturers' prescribing information or standard pharmaceutic reference books is ab-