Journal of the Royal Society of Medicine Volume 85 September 1992
am not, however, impressed by a particular reluctance of the English to disclose their age, but it is a major problem to get clinic receptionists ofeither gender or any race, to ask new patients being registered about their marital status. Perhaps it does not matter much these days in relation to what people get up to but many women do still prefer to be addressed as Mrs or Miss not Ms. I do however take issue with Qureshi when he says that 'every doctor must ask each patient' for, amongst other things a 'summary ofpast illnesses, menstrual, obstetric and sexual difficulties, treatment used for present and past illnesses, family patterns of disease, social habits and occupational habits'. It may be appropriate to seek information in any or all of these areas in an individual patient but I am sure neither Dr Qureshi himself nor any of your readers practices what Qureshi here preaches'. Tyro medical students by instinct and mature clinicians by experience try to reach a diagnosis by a process of hypothesis generation and testing2. However for senior medical students and recently qualified doctors this approach tends to be replaced by a strategy of 'diagnosis by exhaustion'3 thanks to medical school teaching of exhaustive and defensive history taking4. Clinical facts are useful only if they can be employed in solving clinical problems5. Transcultural consultations, as Dr Qureshi stresses, are fraught enough with potential pitfalls thanks to linguistic barriers. There is certainly no place for undirected routine history taking which, by adding verbiage, will increase the chances of misunderstanding and misdirected effort. Whittington Hospital, B I HOFFBRAND Archway Wing, Highgate Hill, London N19 5NF
References 1 Kassirer P. Teaching clinical medicine by iterative hypothesis testing: let's preach what we practice. NEngl J Med 1983;309:921-3 2 Elstein AS, Shulman LS, Sprafka SA. Medical problem solving: an analysis of clinical reasoning. Cambridge, Mass: Harvard University Press, 1978 3 Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical epidemiology. A basic science for clinical medicine; 2nd edn. Boston: Little, Brown & Co. 1991:10 4 HofTbrand BI. Away with the system review: a plea for parsimony. BMJ 1989;298:817-19 5 Schwartz WB. Decision analysis: a look at the chief complaints. N Engl J Med 1979;300:556-9
Does atmospheric nitrous oxide (N20) affect the perception of energy and mood? With reference to the interesting papers by Wood and co-workers (April 1992 JRSM, pp 191 and 195), may I draw attention to an environmental agent, which appears not to have yet been considered in this connection. One of the trace gases present in the atmosphere is nitrous oxide (N20), known as 'laughing gas', which is used as anaesthetic, especially in paediatric dentistry'. It is present in parts per billion; the reported values, estimated in the samples of air taken every January at the South Pole and in the Pacific Northwest, ranged from ca. 297 to 307 ppb, within the decade from 1975 to 1985, and appeared to be almost the same in both localities2. No data
appear to exist on the concentrations of nitrous oxide, and their potential variations in the environment, under the influence of, for example, the sun's radiation, or in industrial areas. It would be of interest to know whether this simple chemical may be involved in the changes of mood, and in the feeling of wellbeing, as soon as the sun emerges from behind the clouds. Certain people are more sensitive to such change than others, but sensitivity to nitrous oxide can vary even in different strains of rats3, and may be related to the concentrations of cobalamin and folates in the body4. While exposure to high concentrations of nitrous oxide has been studied5, the effects of exposure to the range of concentrations present in the atmosphere, are yet to be investigated. Or is this only my ignorance of existing data? I would appreciate information on this point. 15 Birdhurst Court R SCHOENTAL Woodcote Road, Wallington SM6 OPG
References 1 Atkinson RS, Boulton TB. The history of anaesthesia (ICSS 134). London: Royal Society of Medicine Services, 1989 2 Rasmussen RA, Khalil MAK. Atmospheric trace gases: trends and distribution over the last decade. Science 1986;232:1623-4 3 Green CD. Strain sensitivity of rats to nitrous oxide. Anesth Analg 1968;47:508-14 4 Chanarin I. The effects of nitrous oxide on cobalamins, folates and on related events. CRC Crit Rev Toxicol 1982;10:179-213 5 Ermens AAM, Schoester M, Spijkers LJM, Lindemans J, Abels J. Toxicity of methotrexate in rats preexposed to nitrous oxide. Cancer Res 1989;49:6337-6341
Healthcare workers and hepatitis B I refer to a letter by Anand and Myles (April 1992 JRSM, p 246) discussing how to deal with healthcare workers who develop hepatitis B after their failure to develop antibodies to HBsAg following vaccination with the standard three doses of vaccine. The letter suggests that about 10% of vaccinees fail to respond and may lose their careers if subsequently exposed to the virus and develop the carrier state. I would draw your readers' attention to the work of Criske, Bock and Clemens" 2 which describes work on 72 vaccinees who were low or non-responders after three doses of vaccine. All of the initially low responders developed antibodies to the 1000 iu/l level (which will protect for several years) after a maximum of four further doses of 20 ,ig of vaccine. Of the initial non-responders (n=26) 75% seroconverted after three further doses and all of the remainder seroconverted but one required a total of 13 doses. These figures suggest that no health care worker need permanently be without protection against hepatitis B. K M O'SULLIVAN
Head of Therapeutics Intercontinental Medical Department SmithKline Beecham Pharmaceuticals Brentford TW8 9BD
References 1 Criske HW, et aL Abst. 301, 1990 Int. Symp. Viral Hepatitis & Liver disease, April 4-8 1990 Houston, Texas, USA 2 Criske HW, et al. Arbeitsmed Sozialmed Preventivmed 1990;25:421-2
587
am not, however, impressed by a particular reluctance of the English to disclose their age, but it is a major problem to get clinic receptionists ofeither gender or any race, to ask new patients being registered about their marital status. Perhaps it does not matter much these days in relation to what people get up to but many women do still prefer to be addressed as Mrs or Miss not Ms. I do however take issue with Qureshi when he says that 'every doctor must ask each patient' for, amongst other things a 'summary ofpast illnesses, menstrual, obstetric and sexual difficulties, treatment used for present and past illnesses, family patterns of disease, social habits and occupational habits'. It may be appropriate to seek information in any or all of these areas in an individual patient but I am sure neither Dr Qureshi himself nor any of your readers practices what Qureshi here preaches'. Tyro medical students by instinct and mature clinicians by experience try to reach a diagnosis by a process of hypothesis generation and testing2. However for senior medical students and recently qualified doctors this approach tends to be replaced by a strategy of 'diagnosis by exhaustion'3 thanks to medical school teaching of exhaustive and defensive history taking4. Clinical facts are useful only if they can be employed in solving clinical problems5. Transcultural consultations, as Dr Qureshi stresses, are fraught enough with potential pitfalls thanks to linguistic barriers. There is certainly no place for undirected routine history taking which, by adding verbiage, will increase the chances of misunderstanding and misdirected effort. Whittington Hospital, B I HOFFBRAND Archway Wing, Highgate Hill, London N19 5NF
References 1 Kassirer P. Teaching clinical medicine by iterative hypothesis testing: let's preach what we practice. NEngl J Med 1983;309:921-3 2 Elstein AS, Shulman LS, Sprafka SA. Medical problem solving: an analysis of clinical reasoning. Cambridge, Mass: Harvard University Press, 1978 3 Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical epidemiology. A basic science for clinical medicine; 2nd edn. Boston: Little, Brown & Co. 1991:10 4 HofTbrand BI. Away with the system review: a plea for parsimony. BMJ 1989;298:817-19 5 Schwartz WB. Decision analysis: a look at the chief complaints. N Engl J Med 1979;300:556-9
Does atmospheric nitrous oxide (N20) affect the perception of energy and mood? With reference to the interesting papers by Wood and co-workers (April 1992 JRSM, pp 191 and 195), may I draw attention to an environmental agent, which appears not to have yet been considered in this connection. One of the trace gases present in the atmosphere is nitrous oxide (N20), known as 'laughing gas', which is used as anaesthetic, especially in paediatric dentistry'. It is present in parts per billion; the reported values, estimated in the samples of air taken every January at the South Pole and in the Pacific Northwest, ranged from ca. 297 to 307 ppb, within the decade from 1975 to 1985, and appeared to be almost the same in both localities2. No data
appear to exist on the concentrations of nitrous oxide, and their potential variations in the environment, under the influence of, for example, the sun's radiation, or in industrial areas. It would be of interest to know whether this simple chemical may be involved in the changes of mood, and in the feeling of wellbeing, as soon as the sun emerges from behind the clouds. Certain people are more sensitive to such change than others, but sensitivity to nitrous oxide can vary even in different strains of rats3, and may be related to the concentrations of cobalamin and folates in the body4. While exposure to high concentrations of nitrous oxide has been studied5, the effects of exposure to the range of concentrations present in the atmosphere, are yet to be investigated. Or is this only my ignorance of existing data? I would appreciate information on this point. 15 Birdhurst Court R SCHOENTAL Woodcote Road, Wallington SM6 OPG
References 1 Atkinson RS, Boulton TB. The history of anaesthesia (ICSS 134). London: Royal Society of Medicine Services, 1989 2 Rasmussen RA, Khalil MAK. Atmospheric trace gases: trends and distribution over the last decade. Science 1986;232:1623-4 3 Green CD. Strain sensitivity of rats to nitrous oxide. Anesth Analg 1968;47:508-14 4 Chanarin I. The effects of nitrous oxide on cobalamins, folates and on related events. CRC Crit Rev Toxicol 1982;10:179-213 5 Ermens AAM, Schoester M, Spijkers LJM, Lindemans J, Abels J. Toxicity of methotrexate in rats preexposed to nitrous oxide. Cancer Res 1989;49:6337-6341
Healthcare workers and hepatitis B I refer to a letter by Anand and Myles (April 1992 JRSM, p 246) discussing how to deal with healthcare workers who develop hepatitis B after their failure to develop antibodies to HBsAg following vaccination with the standard three doses of vaccine. The letter suggests that about 10% of vaccinees fail to respond and may lose their careers if subsequently exposed to the virus and develop the carrier state. I would draw your readers' attention to the work of Criske, Bock and Clemens" 2 which describes work on 72 vaccinees who were low or non-responders after three doses of vaccine. All of the initially low responders developed antibodies to the 1000 iu/l level (which will protect for several years) after a maximum of four further doses of 20 ,ig of vaccine. Of the initial non-responders (n=26) 75% seroconverted after three further doses and all of the remainder seroconverted but one required a total of 13 doses. These figures suggest that no health care worker need permanently be without protection against hepatitis B. K M O'SULLIVAN
Head of Therapeutics Intercontinental Medical Department SmithKline Beecham Pharmaceuticals Brentford TW8 9BD
References 1 Criske HW, et aL Abst. 301, 1990 Int. Symp. Viral Hepatitis & Liver disease, April 4-8 1990 Houston, Texas, USA 2 Criske HW, et al. Arbeitsmed Sozialmed Preventivmed 1990;25:421-2
587
