the figures provided we calculated that the specificity of the sign of rectal tenderness to the right in this group of patients was 72%. This is higher than the specificities of the three commonest other abdominal findings related to final diagnosis -namely, tenderness in the right lower quadrant (specificty= 17%), guarding (58%), and rebound tenderness (62%). Abdominal rigidity has a specificity of 98% but is present in only 6% of the sample, thereby limiting its usefulness. Our third point arises from the authors' statement that in patients with pain in the right lower quadrant of the abdomen "rectal examination... should not be part of the examination performed by a general practitioner before referral to hospital." This statement may be true for routine rectal examinations, but we do not think that it is possible to extrapolate the findings of this hospital based study to arrive at such a dogmatic statement on how general practitioners should be assessing their patients. Patients with abdominal pain seen by their general practitioners are assessed in more ways than the ones mentioned in this paper, and the incidence of appendicitis will be much lower than in this paper. For example, in 1988 in our practice of about 7000 patients we saw 474 patients with a new problem of abdominal pain and six patients with appendicitis. The patients referred to hospital by their general practitioners had an incidence of appendicitis of 37%, and whether rectal examination played a part in obtaining this high incidence are the logical next areas to be investigated. Any studies assessing the value of symptoms or signs need to take into account that doctors seeing early undifferentiated disease may use the same symptoms and signs in different ways from doctors seeing an already filtered population. PAUL KINNERSLEY JONATHAN RICHARDS CLARE WILKINSON PENNY OWEN Department of General Practice, University of Wales College of Medicine, Cardiff CF3 7PN

gonadotrophin. Reijenders et al did not administer exogenous human chorionic gonadotrophin in their study but looked at the effect of 17 cahydroxyprogesterone caproate on several variables including human chorionic gonadotrophin con-. centrations.2 These did not change after caproate was given. Following Harrison's study,' we have been administering 10 000 IU human chorionic gonadotrophin weekly throughout the first trimester of pregnancy to women who have had two or more consecutive miscarriages. We aimed at investigating the immunological effect of human chorionic gonadotrophin as it may have acted as an immunosuppressant. Preliminary results from our research into T cell subset studies, response of peripheral blood lymphocytes to mitogen stimulation, concentrations of interleukin 2 receptor and interleukin 2, and B cell studies suggest that in 20 women who received human chorionic gonadotrophin, abnormal immunological variables returned to normal by the end of the course of treatment when compared with normal primigravidas in the first trimester of pregnancy. Before the treatment a significantly lower concentration of interleukin 2, higher concentration of interleukin 2 receptor, lower response to various mitogens, and higher production of immunoglobulin was found (unpublished data). Our overall success rate is 80% with this treatment. The mode of action is not clear but may be hormonal, acting through the corpus luteum, or immunosuppressive. We hope that further research will show if human chorionic gonadotrophin is of benefit to these women. M A MAcLEAN R WILSON J J WALKER Royal Infirmary, Glasgow G4 OSF 1 Regan L. Recurrent miscarriage. BMJ 1991;302:543-4.

(9 March.) 1 Dixon JM, Elton RA, Rainey JB, Macleod DAD. Rectal examination in patients with pain in the right lower quadrant of the abdomen. BMJ 1991;302:386-8. (16 Februarv.)

SIR,-Recommendations by Mr J M Dixon and colleagues that doctors should be much more selective before performing rectal examination in patients suspected of having acute appendicitis contrast (as Mr Dixon and colleagues acknowledge) with many standard texts.' I recently carried out a prospective study of 80 consecutive patients of all ages referred by general practitioners to one surgical unit with suspected acute appendicitis. Rectal examination had been performed by general practitioners on 24 patients overall and in 11 of 14 (79%) aged over 50 and 13 of 66 (20%) aged 50 or under, a significant difference (p