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Computers and psychiatric data recording: Rationale and problems of confidentiality
Computers Rationale
and Psychiatric Data Recording: and Problems of Confidentiality
H. B. Kedward, M. R. Eastwood, and F. W. Furlong
T
HE INCREASING AMOUNT of information collected about individual patients by medical and social agencies and the inefficiency of conventional retrieval systems are good reasons for introducing new methods of data collection and processing which would implement the advances made in computer technology. The broad aims of computerization are (1) improvement in information retrieval and, hence, improvement in the clinical management of patients, and (2) the provision of more valid and reliable data for statistical and clinical research. CLINICAL
RECORDS
Although it is claimed that easy access to full medical records is of value in the management of individual patients, the medical benefits of computerized data schemes are not fully known, and there are many ethical and technical difficulties. The main practical problem in introducing a data storage system, other than on a very local scale, is that information is not uniformly collected and varies in quantity and quality from place to place. It is evident that, before setting up a central storage system, information on clinical histories which is considered necessary for later management of patients must be defined and formalized to permit standardised recording. Clinicians, therefore, need to state exactly what they regard as essential information to be held on medical records. It would then be necessary to ensure that this minimal core information is obtained on every patient who comes under psychiatric care. Clearly, in psychiatry it would not be easy to reach agreement on the kind and quality of information to be recorded. The Meyerian assumption, that all aspects of the history of the presenting complaint, family, and personal history must be explored, has long been a tenet of psychiatry. Clinicians are still concerned to elicit all these details but are often uncertain of the relevance of much of the material. Furthermore, many items involve qualitative assessments which lend themselves to summary recording of only low reliability. Once broad agreement had been reached on a limited number of factors to be recorded at interview, the selected information could be translated into a form suitable for computerisation in one of two ways. Physicians could take clinical notes in the usual way but accept a degree of structuring to achieve uniformity, and then assign the task of coding to the records office staff. This method involves less interference with clinical practice and retains the present type of clinical record, but is expensive and increases the possibility of error. Alternatively and more economically, the clinical history could be recorded on preceded forms designed for optical scanning so that the clinician’s observations would be directly available in a form suitable for computerisation. Either method would provide the basis for a system of rapid retrieval from the central service, whenever a patient attended a psychiatric facility, of details of previous From the Section of Psychiatric Epidemiology, Clarke Institute of Psychiatry, Toronto, Canada. H. B. Kedward, M.A., M.D., D.P.M.: Head-Psychiatric Epidemiology; M. R. Eastwood, M.D., M.R.C. Psych., D.P.M.: Assistant Professor; F. W. Furlong, M.D., F.R.C.P.(C): Staff Psychiatrist. 01973 by Grune & Stratton, Inc. Comprehensive Psychiatry, Vol. 14. No. 2 (March/April). 1973
133
134
KEDWARD.
EASTWOOD,
AND
FURLONG
history, including diagnosis and management. The system would forge a link between clinical and research activities and reduce the labor involved in some clinical studies where both clinical and research interviews have been necessary. While the computerised data base is attractive, being speedier and more economical than the traditional retrieval system of writing to other hospitals for summaries of previous admissions, it is essential that the underlying purpose of recording medical information, which is to improve the precision and efficiency of patient care, be kept in mind. RECORDS
FOR
RESEARCH
The availability of comprehensive centralized information would improve the quality of national and regional morbidity statistics. Theoretically, prevalence figures for the various types of psychiatric disorder at both national and local level would be continuously accessible. Such figures, potentially, would reveal fluctuations in psychiatric morbidity at different times within the population. Trends within a country over time for different groupings by age, sex, marital status, social class or ethnic origin would be available, as would differential usage of the psychiatric services by area. This information, already used to predict trends in hospital utilization,’ together with a method of tracing patients to mental hospitals, would permit continuous monitoring of the psychiatric services. The value of this information to Health Service planning bodies would be enormous. In addition to the administrative use of prevalence figures, clinical research by means of prospective studies of individuals with certain diseases or characteristics would be facilitated by reliable medical records on a national scale. Studies of the outcome of psychiatric disorder in hospital and community populationszY3 are examples of valuable work which could be extended and developed, given good national medical records. SPECIAL
PROBLEMS
OF
PSYCHIATRIC
RECORDS
While the two aims of improving the quality of medical care and providing accurate data for research are commendable, there are several practical reasons for urging caution. Psychiatric records differ from the records found, e.g., in internal medicine or general surgery, in that they routinely contain much more intimate details of the patient’s personal history. It is an important difference and the inclusion of this information in a computer data pool is justifiable only if it is necessary for good medical care. There is a greater danger of potentially injurious information being obtained by the unscrupulous than there has been with less efficient systems. Apart from this important ethical issue, the validity and reliability of personal data merit consideration. A patient may not be frank, explicit, or consistent when relating his personal history, and the psychiatrist may fail to ask the prescribed questions, or not record the answers consistently. Furthermore, the predictive validity of many factors is uncertain. Insufficient experimental work has been carried out to show significant associations between experiences or behavior reported to have occurred in childhood and adolescence and adult psychiatric status. It is far from certain, therefore, whether or not there is any real purpose in recording all personal data systematically, whereas there is every reason to study the possible influence of developmental factors by carefully designed prospective research. A satisfactory record system must therefore be flexible and provide space for research enquiries which, in the long term, will point to additional useful factors for routine inclusion in the records.
PSYCHIATRIC
135
DATA RECORDING
Another vexing question is the poor reliability of psychiatric diagnoses. It has been shown4%’ that the present taxonomy is used differently both within and between countries. Therefore, labeling a patient as, say, schizophrenic in one center may be meaningless in terms of the criteria laid down for this diagnosis in another center. It is probable, however, that the reliability of the diagnoses employed in psychiatry will improve as current international studies proceed. Problems of Confidentiality Medical records have traditionally been thought to be confidential by both the profession and the public but absolute confidentiality has never been achieved. Exceptions have to be tolerated in cases of overwhelming social and legal importance. Thus, records may be released at the direction of a court. Also, for practical reasons, absolute medical confidentiality is impossible. Many people are involved in clinical management in psychiatry and clerical staff type and file notes which have been available to a variety of nonmedical personnel, not all of whom have professional training or orientation. In every case there is the justification that the breach of confidentiality is necessary for administrative purposes or, in the case of the medical ancillaries, because of the patient’s interests, or because there is immediate danger to society. Thus the rule of confidentiality is never simple nor all-or-nothing, but rather a principle devoted to the balance between the interests of patient and society. The complication in psychiatry, as opposed to other medical specialties, is that information collected on each patient stresses the family, personal, social, and sexual history. It is clear that the leakage of such material would usually have a greater social impact for the individual than information on, say, the state of his duodenal ulcer. The basic moral issues of confidentiality are the same for automated as for nonautomated records, but additional and menacing dangers arise from the increased efficiency of the computer. Unauthorized use of traditional records is hampered by the-inefficiency of the system. Usually the enquirer must deal with an individual official and gains access to only one record at a time. There has been no easy way to scan many records for a certain attribute. The typist who prepares a letter on a patient is unlikely to be personally acquainted with him. The person who tried to break through the screen of confidentiality, to the disadvantage of the patient, has been hampered by the system; whereas computerization may assist him. There has been public disquiet recently in the United Kingdom regarding credit systems since the disclosure that information from them and from State Taxation Offices had been leaked to unscrupulous persons. Information had been acquired by such methods as bribing former employees of these organizations and gaining access to the data output codes. Techniques for tapping data banks could apply equally well to medical records as to credit ratings. If the recent public concern, expressed in different ways in Britain, Canada, and the United States, created a general suspicion of all forms of automated information storage, medical record computerization could have the opposite effect of that intended. Patients might decline to give physicians as much information about themselves as they have in the past. TECHNICAL
PROBLEMS
An almost unlimited variety of questions may be asked of an information system. Once in possession of a security code, the unscrupulous individual might obtain not only a routine history, but acquire from the computer a given piece of information on
136
KEDWARD.
EASTWOOD.
AND
FURLONG
all patients admitting to certain types of behaviour. The combinations are practically limitless. A rapid display of the requested data is then available. It is the immediate availability of information to the occasional unscrupulous person who gains access to the system which is the threat computerization poses to confidentiality. Many publications stress the importance and relative security of a code number similar to a lock combination that restricts information to authorized persons. It has been suggested6 that identifiable data on specific patients could be made available to one level of authorized persons and that unidentifiable data on groups of patients could be released to other groups. Technical experts, however, writing in their own journals, question the feasibility of absolute security for computer-based information systems. It has been stated: there appears to be a lack of good security of computer systems and their related data bases. This point has been underscored by a series of articles and news items reporting. theft cases involving program manipulation. Management cannot depend upon electronic data processing operations . . . to ensure the security of data bases. .7
One approach to confidentiality was devised in the Camberwell study in London.’ Patients’ names were listed alphabetically on small cards. Clinical and social information was recorded on master cards, each of which also bore the patient’s serial number and address in coded form. The serial numbers were then entered in order in a book and the patients’ names recorded beside their number. Subsequently, the original forms, bearing both names and confidential information, were destroyed. CONCLUSIONS
Technical innovation in medicine can help improve the quality of medical care and provide more accurate data for research. Medical practice has begun to assume some of the features of a consumer industry but will, as a profession, continue to differ from business in the relative importance given to ethical considerations, particularly those bearing on responsibility to patients. Improvements in technology have altered medical practice considerably since the World War II, particularly in the areas of precision of diagnosis and specificity of management. Technical achievement is not the only important factor, however, in the progress of a profession, and a balance has to be struck between the ethics of practice and the nature of the services offered to the public. Screening for disease is an example of techniques outstripping medical knowledgeglrO and the profession is in danger of providing screening services for the public without being able to say whether or not a given individual will benefit if an abnormality is detected. The same can be said of the computerization of medical data in psychiatry. The concept is appealing because automation can provide a rapid retrieval service for clinicians and at the same time yield an abundance of data for research purposes. Against this lies the risk of confidentiality becoming jeopardized and deep concern among the public at the realization that information divulged in the doctor’s consulting room would be placed in a central computer. This could result in a serious loss of confidence in the medical profession by the general public and thereby affect the traditional doctor-patient relationship. The public can only be expected to accept the new approach to data recording if its utility is beyond doubt. Unfortunately, this cannot be claimed for much of the data collected at psychiatric interview, whether to be used for individual patient care decisions at readmission or for statistical purposes.
PSYCHIATRIC
137
DATA RECORDING
The computerization of psychiatric records offers many potential benefits for psychiatric practice and research but studies of reliability and validity are essential before national computerisation schemes for psychiatric records are put into operation. The studies required would be of hard data such as demographic variables, treatment and possibly diagnosis, rather than of soft data like childhood development and personality. Such studies should be carried out in several centers, with coordination of design and method, and the level of agreement between trainee and consultant psychiatrists for the different items should be determined. The likelihood is that, although the reliability of some items may prove to be of a high order, differences due to variations in training and practice will be found between centers, age groups and categories of doctor. Only when the reliability of these items is found to be satisfactory, would it be justifiable to include them in a computer data recording scheme. The system should allow for further development and the inclusion of additional items when these are demonstrated to be relevant and capable of reliable recording. SUMMARY
Increased efficiency in handling medical record data and facilitation of statistical research can be achieved by the use of computers. The application of high speed data handling techniques in medicine poses considerable problems which are perhaps greater in psychiatry than any other speciality. As in medicine generally, items selected for recording must be restricted to questions which may be expected to obtain valid answers with a high degree of interobserver reliability. The personal nature of much of the information obtained at psychiatric interview, and the proportion of qualitative assessments included require particular attention if regional or national data banks for psychiatry are to be both useful and safe. REFERENCES 1. Tooth, G. C., and Brooke, E. M.: Lancet, 1:710, 1961. 2. Greer, S. H., Cawley, R. H.: Natural History of Neurotic Illness. Australian Medical Association Mervyn Archdall Medical Monograph, No. 3, 1966. 3. Hagnell, 0.: Res. Publ. Ass. Res. Nerv. Ment. Dis. 47:22,1969.
dell, R. E., and Gourlay, A. J.: Br. J. Psychiat. 118:629, 1971. 6. Sadana, R.: Unpublished data. 7. Bates, W. S.: Datamation 16:60, 1970. 8. Wing, L., Bramley, C., Hailey, A., Wing, J. K.: Social Psychiatry, 1968, 3, 116.
4. Kreitman, 1961. 5. Copeland,
10. McKeown, T. (Ed.): In Screening for Medical Care. London, Nuffield Provincial Hospitals Trust, 1968.
N.:
J.
Ment.
J. R. M., Cooper,
Sci.
107:876,
M. E., Ken-
9. Wilson, J. M. C., Jungner, G.: W.H.O. Public Health Papers. No. 34, 1968.
and Psychiatric Data Recording: and Problems of Confidentiality
H. B. Kedward, M. R. Eastwood, and F. W. Furlong
T
HE INCREASING AMOUNT of information collected about individual patients by medical and social agencies and the inefficiency of conventional retrieval systems are good reasons for introducing new methods of data collection and processing which would implement the advances made in computer technology. The broad aims of computerization are (1) improvement in information retrieval and, hence, improvement in the clinical management of patients, and (2) the provision of more valid and reliable data for statistical and clinical research. CLINICAL
RECORDS
Although it is claimed that easy access to full medical records is of value in the management of individual patients, the medical benefits of computerized data schemes are not fully known, and there are many ethical and technical difficulties. The main practical problem in introducing a data storage system, other than on a very local scale, is that information is not uniformly collected and varies in quantity and quality from place to place. It is evident that, before setting up a central storage system, information on clinical histories which is considered necessary for later management of patients must be defined and formalized to permit standardised recording. Clinicians, therefore, need to state exactly what they regard as essential information to be held on medical records. It would then be necessary to ensure that this minimal core information is obtained on every patient who comes under psychiatric care. Clearly, in psychiatry it would not be easy to reach agreement on the kind and quality of information to be recorded. The Meyerian assumption, that all aspects of the history of the presenting complaint, family, and personal history must be explored, has long been a tenet of psychiatry. Clinicians are still concerned to elicit all these details but are often uncertain of the relevance of much of the material. Furthermore, many items involve qualitative assessments which lend themselves to summary recording of only low reliability. Once broad agreement had been reached on a limited number of factors to be recorded at interview, the selected information could be translated into a form suitable for computerisation in one of two ways. Physicians could take clinical notes in the usual way but accept a degree of structuring to achieve uniformity, and then assign the task of coding to the records office staff. This method involves less interference with clinical practice and retains the present type of clinical record, but is expensive and increases the possibility of error. Alternatively and more economically, the clinical history could be recorded on preceded forms designed for optical scanning so that the clinician’s observations would be directly available in a form suitable for computerisation. Either method would provide the basis for a system of rapid retrieval from the central service, whenever a patient attended a psychiatric facility, of details of previous From the Section of Psychiatric Epidemiology, Clarke Institute of Psychiatry, Toronto, Canada. H. B. Kedward, M.A., M.D., D.P.M.: Head-Psychiatric Epidemiology; M. R. Eastwood, M.D., M.R.C. Psych., D.P.M.: Assistant Professor; F. W. Furlong, M.D., F.R.C.P.(C): Staff Psychiatrist. 01973 by Grune & Stratton, Inc. Comprehensive Psychiatry, Vol. 14. No. 2 (March/April). 1973
133
134
KEDWARD.
EASTWOOD,
AND
FURLONG
history, including diagnosis and management. The system would forge a link between clinical and research activities and reduce the labor involved in some clinical studies where both clinical and research interviews have been necessary. While the computerised data base is attractive, being speedier and more economical than the traditional retrieval system of writing to other hospitals for summaries of previous admissions, it is essential that the underlying purpose of recording medical information, which is to improve the precision and efficiency of patient care, be kept in mind. RECORDS
FOR
RESEARCH
The availability of comprehensive centralized information would improve the quality of national and regional morbidity statistics. Theoretically, prevalence figures for the various types of psychiatric disorder at both national and local level would be continuously accessible. Such figures, potentially, would reveal fluctuations in psychiatric morbidity at different times within the population. Trends within a country over time for different groupings by age, sex, marital status, social class or ethnic origin would be available, as would differential usage of the psychiatric services by area. This information, already used to predict trends in hospital utilization,’ together with a method of tracing patients to mental hospitals, would permit continuous monitoring of the psychiatric services. The value of this information to Health Service planning bodies would be enormous. In addition to the administrative use of prevalence figures, clinical research by means of prospective studies of individuals with certain diseases or characteristics would be facilitated by reliable medical records on a national scale. Studies of the outcome of psychiatric disorder in hospital and community populationszY3 are examples of valuable work which could be extended and developed, given good national medical records. SPECIAL
PROBLEMS
OF
PSYCHIATRIC
RECORDS
While the two aims of improving the quality of medical care and providing accurate data for research are commendable, there are several practical reasons for urging caution. Psychiatric records differ from the records found, e.g., in internal medicine or general surgery, in that they routinely contain much more intimate details of the patient’s personal history. It is an important difference and the inclusion of this information in a computer data pool is justifiable only if it is necessary for good medical care. There is a greater danger of potentially injurious information being obtained by the unscrupulous than there has been with less efficient systems. Apart from this important ethical issue, the validity and reliability of personal data merit consideration. A patient may not be frank, explicit, or consistent when relating his personal history, and the psychiatrist may fail to ask the prescribed questions, or not record the answers consistently. Furthermore, the predictive validity of many factors is uncertain. Insufficient experimental work has been carried out to show significant associations between experiences or behavior reported to have occurred in childhood and adolescence and adult psychiatric status. It is far from certain, therefore, whether or not there is any real purpose in recording all personal data systematically, whereas there is every reason to study the possible influence of developmental factors by carefully designed prospective research. A satisfactory record system must therefore be flexible and provide space for research enquiries which, in the long term, will point to additional useful factors for routine inclusion in the records.
PSYCHIATRIC
135
DATA RECORDING
Another vexing question is the poor reliability of psychiatric diagnoses. It has been shown4%’ that the present taxonomy is used differently both within and between countries. Therefore, labeling a patient as, say, schizophrenic in one center may be meaningless in terms of the criteria laid down for this diagnosis in another center. It is probable, however, that the reliability of the diagnoses employed in psychiatry will improve as current international studies proceed. Problems of Confidentiality Medical records have traditionally been thought to be confidential by both the profession and the public but absolute confidentiality has never been achieved. Exceptions have to be tolerated in cases of overwhelming social and legal importance. Thus, records may be released at the direction of a court. Also, for practical reasons, absolute medical confidentiality is impossible. Many people are involved in clinical management in psychiatry and clerical staff type and file notes which have been available to a variety of nonmedical personnel, not all of whom have professional training or orientation. In every case there is the justification that the breach of confidentiality is necessary for administrative purposes or, in the case of the medical ancillaries, because of the patient’s interests, or because there is immediate danger to society. Thus the rule of confidentiality is never simple nor all-or-nothing, but rather a principle devoted to the balance between the interests of patient and society. The complication in psychiatry, as opposed to other medical specialties, is that information collected on each patient stresses the family, personal, social, and sexual history. It is clear that the leakage of such material would usually have a greater social impact for the individual than information on, say, the state of his duodenal ulcer. The basic moral issues of confidentiality are the same for automated as for nonautomated records, but additional and menacing dangers arise from the increased efficiency of the computer. Unauthorized use of traditional records is hampered by the-inefficiency of the system. Usually the enquirer must deal with an individual official and gains access to only one record at a time. There has been no easy way to scan many records for a certain attribute. The typist who prepares a letter on a patient is unlikely to be personally acquainted with him. The person who tried to break through the screen of confidentiality, to the disadvantage of the patient, has been hampered by the system; whereas computerization may assist him. There has been public disquiet recently in the United Kingdom regarding credit systems since the disclosure that information from them and from State Taxation Offices had been leaked to unscrupulous persons. Information had been acquired by such methods as bribing former employees of these organizations and gaining access to the data output codes. Techniques for tapping data banks could apply equally well to medical records as to credit ratings. If the recent public concern, expressed in different ways in Britain, Canada, and the United States, created a general suspicion of all forms of automated information storage, medical record computerization could have the opposite effect of that intended. Patients might decline to give physicians as much information about themselves as they have in the past. TECHNICAL
PROBLEMS
An almost unlimited variety of questions may be asked of an information system. Once in possession of a security code, the unscrupulous individual might obtain not only a routine history, but acquire from the computer a given piece of information on
136
KEDWARD.
EASTWOOD.
AND
FURLONG
all patients admitting to certain types of behaviour. The combinations are practically limitless. A rapid display of the requested data is then available. It is the immediate availability of information to the occasional unscrupulous person who gains access to the system which is the threat computerization poses to confidentiality. Many publications stress the importance and relative security of a code number similar to a lock combination that restricts information to authorized persons. It has been suggested6 that identifiable data on specific patients could be made available to one level of authorized persons and that unidentifiable data on groups of patients could be released to other groups. Technical experts, however, writing in their own journals, question the feasibility of absolute security for computer-based information systems. It has been stated: there appears to be a lack of good security of computer systems and their related data bases. This point has been underscored by a series of articles and news items reporting. theft cases involving program manipulation. Management cannot depend upon electronic data processing operations . . . to ensure the security of data bases. .7
One approach to confidentiality was devised in the Camberwell study in London.’ Patients’ names were listed alphabetically on small cards. Clinical and social information was recorded on master cards, each of which also bore the patient’s serial number and address in coded form. The serial numbers were then entered in order in a book and the patients’ names recorded beside their number. Subsequently, the original forms, bearing both names and confidential information, were destroyed. CONCLUSIONS
Technical innovation in medicine can help improve the quality of medical care and provide more accurate data for research. Medical practice has begun to assume some of the features of a consumer industry but will, as a profession, continue to differ from business in the relative importance given to ethical considerations, particularly those bearing on responsibility to patients. Improvements in technology have altered medical practice considerably since the World War II, particularly in the areas of precision of diagnosis and specificity of management. Technical achievement is not the only important factor, however, in the progress of a profession, and a balance has to be struck between the ethics of practice and the nature of the services offered to the public. Screening for disease is an example of techniques outstripping medical knowledgeglrO and the profession is in danger of providing screening services for the public without being able to say whether or not a given individual will benefit if an abnormality is detected. The same can be said of the computerization of medical data in psychiatry. The concept is appealing because automation can provide a rapid retrieval service for clinicians and at the same time yield an abundance of data for research purposes. Against this lies the risk of confidentiality becoming jeopardized and deep concern among the public at the realization that information divulged in the doctor’s consulting room would be placed in a central computer. This could result in a serious loss of confidence in the medical profession by the general public and thereby affect the traditional doctor-patient relationship. The public can only be expected to accept the new approach to data recording if its utility is beyond doubt. Unfortunately, this cannot be claimed for much of the data collected at psychiatric interview, whether to be used for individual patient care decisions at readmission or for statistical purposes.
PSYCHIATRIC
137
DATA RECORDING
The computerization of psychiatric records offers many potential benefits for psychiatric practice and research but studies of reliability and validity are essential before national computerisation schemes for psychiatric records are put into operation. The studies required would be of hard data such as demographic variables, treatment and possibly diagnosis, rather than of soft data like childhood development and personality. Such studies should be carried out in several centers, with coordination of design and method, and the level of agreement between trainee and consultant psychiatrists for the different items should be determined. The likelihood is that, although the reliability of some items may prove to be of a high order, differences due to variations in training and practice will be found between centers, age groups and categories of doctor. Only when the reliability of these items is found to be satisfactory, would it be justifiable to include them in a computer data recording scheme. The system should allow for further development and the inclusion of additional items when these are demonstrated to be relevant and capable of reliable recording. SUMMARY
Increased efficiency in handling medical record data and facilitation of statistical research can be achieved by the use of computers. The application of high speed data handling techniques in medicine poses considerable problems which are perhaps greater in psychiatry than any other speciality. As in medicine generally, items selected for recording must be restricted to questions which may be expected to obtain valid answers with a high degree of interobserver reliability. The personal nature of much of the information obtained at psychiatric interview, and the proportion of qualitative assessments included require particular attention if regional or national data banks for psychiatry are to be both useful and safe. REFERENCES 1. Tooth, G. C., and Brooke, E. M.: Lancet, 1:710, 1961. 2. Greer, S. H., Cawley, R. H.: Natural History of Neurotic Illness. Australian Medical Association Mervyn Archdall Medical Monograph, No. 3, 1966. 3. Hagnell, 0.: Res. Publ. Ass. Res. Nerv. Ment. Dis. 47:22,1969.
dell, R. E., and Gourlay, A. J.: Br. J. Psychiat. 118:629, 1971. 6. Sadana, R.: Unpublished data. 7. Bates, W. S.: Datamation 16:60, 1970. 8. Wing, L., Bramley, C., Hailey, A., Wing, J. K.: Social Psychiatry, 1968, 3, 116.
4. Kreitman, 1961. 5. Copeland,
10. McKeown, T. (Ed.): In Screening for Medical Care. London, Nuffield Provincial Hospitals Trust, 1968.
N.:
J.
Ment.
J. R. M., Cooper,
Sci.
107:876,
M. E., Ken-
9. Wilson, J. M. C., Jungner, G.: W.H.O. Public Health Papers. No. 34, 1968.