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Bone density screening for osteoporosis
LETTERS to the EDITOR
Bone
density screening for osteoporosis
SIR,-In 1968 Wilson and Jungner1 wrote a classic paper on screening for disease. At the time, the model for successful screening was control of communicable diseases such as tuberculosis and syphilis by detecting early cases, and Wilson and Jungner explored the extension of this case to non-communicable disease. They were enthusiastic about prevention by general practitioners but were cautious about major screening programmes, pointing out that many characteristics (eg, blood pressure) were continuously distributed in the population, not bimodally distributed as the ideal screening model supposes. They mentioned ethical dilemmas and uncertainty about the economics of early disease detection. Two decades on, the prevention of osteoporosis in women by screening for low bone density is being urged. This approach is gaining ground in the commercial sector, and the National Osteoporosis Society has been campaigning for bone screening to be freely available on the NHS. The Department of Health has given no policy guidance. Dr Tobias and colleagues (June 16, p 1471) argue that because drugs are available for the prevention of osteoporosis, and because bone densitometry by dual energy X-ray absorption (DEXA) is feasible, screening should be provided. However, we suspect that Wilson and Jungner would have discounted osteoporosis, on two grounds. Bone density is not bimodally distributed, and true presymptomatic cases cannot easily be identifiedLongitudinal studies3-S do suggest an association between bone density and risk of fracture, but a fracture threshold has been difficult to define. Although they demonstrate an aetiological role for osteoporosis in age-related fractures, these studies do not make the case for screening. The second reason for the dismissal of screening is that benefit from preventive measures, most notably hormone replacement therapy (HRT), is not limited to women with low bone density.*’ HRT should be considered for any menopausal
woman.
The wealth of adverse comment on established or newly introduced screening programmes contrasts with the silence about osteoporosis screening. The potential for cervical screening to be effective has been demonstrated in British Columbia, but the programme in the UK has been severely criticised. Roberts et aF estimated that it costs c300 000 to save a life. Posner and Vessey’s8 account of the anxiety experienced by the many women who have abnormal cervical smear tests but in whom serious disease would not ensue is a reminder of the effect screening programmes have on those other than the ones benefiting. Dr Maureen Roberts, director of the Edinburgh Breast Screening Project, while herself dying of
breast cancer, wrote reluctantly but honestly of her misgivings about the benefits of breast screening and of the political nature of the decision to introduce the UK programme.9 How then is osteoporosis screening gaining credibility and attracting so little adverse comment? Confusion over the theory of screening may be part of the explanation. The ten-point checklist (table) known as "Wilson’s criteria" was introduced as "an attempt to elaborate at least some ... guides to planning case fmding". For "ease of description rather than dogma" Wilson and Jungner called these points collectively "principles". Focusing on these guidelines in the order they were originally set down may lead to the conclusion that any important health problem (point 1) which might be preventable (point 2) and which develops slowly (point 4) is a candidate for screening if there is some measurable characteristic of the disease process (point 5). The debate then moves rapidly on to details of the test and the treatment and to issues such as who to screen and how often. The question of whether any good will result and at what cost gets lost. Other factors which may, unwittingly, be helping to sustain the "screening juggernaut" include a genuine enthusiasm for prevention, which is more easily channelled into secondary prevention through screening than into the diffuse activities necessary for primary prevention. Also there is the commercial interest in expanding screening. Once women have been persuaded to have bone density measurements at age 50 there will be a market for repeated measurements in the future and for investigating those whose measurements are deemed abnormal. Little is gained from challenging proposed screening activities, especially when interest in the issue is bringing in research funding. Public enthusiasm for screening means votes for politicians who support such activities. We do not wish to see prevention or research given low priority, but uncritical advocacy of screening may ultimately damage both. Osteoporosis sufferers (men and women) deserve better than they will get from massive investment in bone density screening. DEXA machines are a great step forward in the technology for bone density measurement and, if used for research, could provide answers to many of the questions about the causes and treatment of
osteoporosis. Southmead Hospital, Bristol BS10 5NB, UK
ANGELA E. RAFFLE
Bristol Royal
CYRUS COOPER
Infirmary
Principles and practice of screening for disease. Publ Health Pap 1968; no 34. Melton LJ, Kan SJ, Wahner HW, Riggs BL. Lifetime fracture risk: an approach to hip fracture risk assessment based on bone mineral density and age. J Clin Epidemiol
1. Wilson JMG, Jungner G.
2
1988, 41: 985-94.
Cummings SR, Black DM, Nevitt MC, et al. The study of Osteoporotic Fractures Research Group: appendicular bone density and age predict hip fracture m women. JAMA 1990; 263: 665-68. 4. Hui SL, Slemenda CW, Johnston CC. Baseline measurement of bone mass predicts 3
WILSON AND JUNGNER’S PRINCIPLES
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Condition sought an important health problem Accepted treatment for patients with disease Facilities for diagnosis and treatment available Recognisable latent or early symptomatic stage Suitable test or examination Test acceptable to population Natural history of condition adequately understood Agreed policy on whom to treat Costs (including those of diagnosis and treatment) economically balanced in relation to expenditure on medical care as a whole Continuing process, not "once and for all" project
fracture in white women. Ann Intern Med 1989, 111: 355-61. 5. Wasnich RD, Ross PD, Heilbrun HK, Vogel JM. Prediction of postmenopausal fracture nsk with use of bone mineral measurements. Am J Obstet Gynecol 1985; 153: 745-51. 6. Christiansen C, Rodbro P. Does postmenopausal bone loss respond to oestrogen replacement therapy independent of bone loss rate? Calcif Tissue Int 1983; 35: 720-22 7. Roberts CJ, Farrow SC, Charny MC How much can the NHS afford to spend to save a life or avoid a severe disability. Lancet 1985; i: 89-91. 8. Posner T, Vessey M. Prevention of cervical cancer: the patient’s view. London. King’s Fund, 1989. 9. Roberts MM Breast screening. time for a rethink? Br Med J1989; 299: 1153-55.
Bone
density screening for osteoporosis
SIR,-In 1968 Wilson and Jungner1 wrote a classic paper on screening for disease. At the time, the model for successful screening was control of communicable diseases such as tuberculosis and syphilis by detecting early cases, and Wilson and Jungner explored the extension of this case to non-communicable disease. They were enthusiastic about prevention by general practitioners but were cautious about major screening programmes, pointing out that many characteristics (eg, blood pressure) were continuously distributed in the population, not bimodally distributed as the ideal screening model supposes. They mentioned ethical dilemmas and uncertainty about the economics of early disease detection. Two decades on, the prevention of osteoporosis in women by screening for low bone density is being urged. This approach is gaining ground in the commercial sector, and the National Osteoporosis Society has been campaigning for bone screening to be freely available on the NHS. The Department of Health has given no policy guidance. Dr Tobias and colleagues (June 16, p 1471) argue that because drugs are available for the prevention of osteoporosis, and because bone densitometry by dual energy X-ray absorption (DEXA) is feasible, screening should be provided. However, we suspect that Wilson and Jungner would have discounted osteoporosis, on two grounds. Bone density is not bimodally distributed, and true presymptomatic cases cannot easily be identifiedLongitudinal studies3-S do suggest an association between bone density and risk of fracture, but a fracture threshold has been difficult to define. Although they demonstrate an aetiological role for osteoporosis in age-related fractures, these studies do not make the case for screening. The second reason for the dismissal of screening is that benefit from preventive measures, most notably hormone replacement therapy (HRT), is not limited to women with low bone density.*’ HRT should be considered for any menopausal
woman.
The wealth of adverse comment on established or newly introduced screening programmes contrasts with the silence about osteoporosis screening. The potential for cervical screening to be effective has been demonstrated in British Columbia, but the programme in the UK has been severely criticised. Roberts et aF estimated that it costs c300 000 to save a life. Posner and Vessey’s8 account of the anxiety experienced by the many women who have abnormal cervical smear tests but in whom serious disease would not ensue is a reminder of the effect screening programmes have on those other than the ones benefiting. Dr Maureen Roberts, director of the Edinburgh Breast Screening Project, while herself dying of
breast cancer, wrote reluctantly but honestly of her misgivings about the benefits of breast screening and of the political nature of the decision to introduce the UK programme.9 How then is osteoporosis screening gaining credibility and attracting so little adverse comment? Confusion over the theory of screening may be part of the explanation. The ten-point checklist (table) known as "Wilson’s criteria" was introduced as "an attempt to elaborate at least some ... guides to planning case fmding". For "ease of description rather than dogma" Wilson and Jungner called these points collectively "principles". Focusing on these guidelines in the order they were originally set down may lead to the conclusion that any important health problem (point 1) which might be preventable (point 2) and which develops slowly (point 4) is a candidate for screening if there is some measurable characteristic of the disease process (point 5). The debate then moves rapidly on to details of the test and the treatment and to issues such as who to screen and how often. The question of whether any good will result and at what cost gets lost. Other factors which may, unwittingly, be helping to sustain the "screening juggernaut" include a genuine enthusiasm for prevention, which is more easily channelled into secondary prevention through screening than into the diffuse activities necessary for primary prevention. Also there is the commercial interest in expanding screening. Once women have been persuaded to have bone density measurements at age 50 there will be a market for repeated measurements in the future and for investigating those whose measurements are deemed abnormal. Little is gained from challenging proposed screening activities, especially when interest in the issue is bringing in research funding. Public enthusiasm for screening means votes for politicians who support such activities. We do not wish to see prevention or research given low priority, but uncritical advocacy of screening may ultimately damage both. Osteoporosis sufferers (men and women) deserve better than they will get from massive investment in bone density screening. DEXA machines are a great step forward in the technology for bone density measurement and, if used for research, could provide answers to many of the questions about the causes and treatment of
osteoporosis. Southmead Hospital, Bristol BS10 5NB, UK
ANGELA E. RAFFLE
Bristol Royal
CYRUS COOPER
Infirmary
Principles and practice of screening for disease. Publ Health Pap 1968; no 34. Melton LJ, Kan SJ, Wahner HW, Riggs BL. Lifetime fracture risk: an approach to hip fracture risk assessment based on bone mineral density and age. J Clin Epidemiol
1. Wilson JMG, Jungner G.
2
1988, 41: 985-94.
Cummings SR, Black DM, Nevitt MC, et al. The study of Osteoporotic Fractures Research Group: appendicular bone density and age predict hip fracture m women. JAMA 1990; 263: 665-68. 4. Hui SL, Slemenda CW, Johnston CC. Baseline measurement of bone mass predicts 3
WILSON AND JUNGNER’S PRINCIPLES
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Condition sought an important health problem Accepted treatment for patients with disease Facilities for diagnosis and treatment available Recognisable latent or early symptomatic stage Suitable test or examination Test acceptable to population Natural history of condition adequately understood Agreed policy on whom to treat Costs (including those of diagnosis and treatment) economically balanced in relation to expenditure on medical care as a whole Continuing process, not "once and for all" project
fracture in white women. Ann Intern Med 1989, 111: 355-61. 5. Wasnich RD, Ross PD, Heilbrun HK, Vogel JM. Prediction of postmenopausal fracture nsk with use of bone mineral measurements. Am J Obstet Gynecol 1985; 153: 745-51. 6. Christiansen C, Rodbro P. Does postmenopausal bone loss respond to oestrogen replacement therapy independent of bone loss rate? Calcif Tissue Int 1983; 35: 720-22 7. Roberts CJ, Farrow SC, Charny MC How much can the NHS afford to spend to save a life or avoid a severe disability. Lancet 1985; i: 89-91. 8. Posner T, Vessey M. Prevention of cervical cancer: the patient’s view. London. King’s Fund, 1989. 9. Roberts MM Breast screening. time for a rethink? Br Med J1989; 299: 1153-55.