A comparison of doctor and computer interrogation of patients

A COMPARISON OF DOCTOR AND COMPUTER INTERROGATION OF PATIENTS W. I. CAmt,

MARY NrcHoLsoNt, G. P. C&EAN*, G. WATKINSON’, C. R. EVANStt, JACKIE WlLsONtt, and DAPHNE RUSSELL**

tDepartment of Medicine in Relation to Mathematics and Computing, University of Glasgow, Glasgow (Great Britain) *Gastrointestinal Centre, Southern General Hospital, Glasgow (Great Britain) YtDivision of Computer Science, National Physical Laboratory (Great Britain) **Department of Statistics, University of Newcastle upon Tyne, Newcastle Upon Tyne (Great Britain) (Received: 29 November,

1973)

SUMMARY

were interrogated for the presence of gastrointestinal symptoms by either a doctor-doctor pair or a doctor-computer pair, in each case independently. A study was made of the acceptability of computer interrogation to the patient and the accuracy of the responses elicited was measured by estimating the errors incurred by doctor and by computer using a model based on information theory. Computer interrogation was acceptable to the majority of patients but was less accurate than doctor interrogation.

Patients

SOMMAIRE

Des malades ont Pte’interroges sur l’existence de troubles gastro intestinaux soit par deux medecins, soit par un medecin et un ordinateur et cela de facon independante. Une Prude a PtPfaite sur la validite de I’interrogatoire par ordinateur, et la precision des reponses fournies a et&mesuree en estimant les erreurs commises par les medecins et le calculateur grace a un modele reposant sur la theorie de Enformation. L’interrogatoire par ordinateur s’est montre acceptable dans la majorite des cas, mais avec moins de precisions qutrn examen medical.

INTRODUCTION History-taking doctor

to

gain

is an important insight

into

part

of the medical

the patient

while

examination

he elicits

evidence

as it allows about

the

possible

175 Int. J. Bio-Medical Computing (5) (1974)~_O Applied Science Publishers Ltd, England, 1974 Printed in Great Britain

w. I. CARDet al.

176

diseases. In this paper we are only concerned with the latter activity-how such elements of evidence may be obtained by interrogation. We assume that a patient, to a first approximation, can be regarded as a set of defined symptoms, laboratory findings, etc., each of which contributes to the probability that a disease is present (Good and Card, 1971; Card and Good, 1974). It is convenient to have a generic word for any such element of evidence, and these workers adopted the word ‘indicant’ from Grew (1701). An indicant is a proposition that is ultimately derived from some event within the patient’s body and it is helpful to think of the path between the event, or the patient’s experience of it, and the indicant as an information channel. (This stimulating way of looking at the matter was proposed to us by I. J. Good). This allows us to apply information theory to the analysis of patient interrogation (Abramson, 1963). If interrogation using a computer program were acceptable to the patient, and if the accuracy achieved were comparable to that achieved by a doctor, historical evidence could usefully be collected in this way. A number of studies have been made of this problem in the past (Slack et al., 1966; Mayne et al., 1968; Kanner, 1969; Mayne, 1970; Simmons and Miller, 1970). METHODS

AND PATIENTS

Fourteen symptoms of dyspepsia were chosen and their definition was agreed after discussion between three consultants (Table 1). A proforma was drawn up to be completed for each patient for each interview, whether with a consultant or with the computer. While a consultant could use whatever questions he pleased to elicit the symptom, a program had to be written for the computer interrogation and the questions had to be carefully framed to avoid ambiguity. For example, while ‘vomiting’ is defined as the bringing up of food from the stomach, it does TABLE 1 LIST OF SYMPTOMS 1.

AND AN EXAMPLE

OF A DEFINITION

Episodicpain.

2. Relation to food. 3. Relief of pain from antacids. 4. Nocturnal pain. 5. Post-cibal pain. 6. Post-cibal nausea. 7. Vomiting. 8. Relief of pain from vomiting. 9. Waterbrash. 10. Heartburn. 11. Acid regurgitation, post-cibal. 12. Acid regurgitation, postural. 13. Weight loss. 14. Family history of ulcer. Example of a definition. 4. Nocturnalpain. If the patient wakes up with pain and takes milk, or a snack, or a little warm water, or indigestion medicine, powders or tablets and then gets relief, the symptom is present.

INTERROGATION

177

OF PATIENTS

not only mean this to all our patients, but is also used to describe what should be called ‘retching’. It is therefore necessary to insert a further question into the program, ‘When you vomit, do you bring up food? All questions had to be phrased in more than one way in case the question was not understood the first time it was asked. The automated interrogation program and the terminal equipment were planned in such a way that the whole of the interview was conducted by the computer with no assistance to the patient by medical or nursing staff. This meant that the program had to be fully comprehensible to any patient, and unlikely to provoke difficulty or anxiety. The computer was therefore programmed to explain its purpose to the patient and a number of introductory questions of no medical significance were introduced which allowed the patient to practise button pushing and to adapt to his unusual situation. The style of the conversational exchange was informal and chatty (Table 2). The program was written in BASIC, consisting of approximately 23,000 characters, and was operated through the Honeywell Time Sharing Service via a modified standard teletype terminal. A complete record of the print-out and TABLE 2 EXAMPLE H

ELLO.

THl.5

HELP

DOCTORS

MUCH

LIKE

YOU

PREPARtD UOULD LIKE THE

NOT* HELP

BUTTON. THANKS FIND

THIS

SHOULD

NOY

ARE

OF

GOOD. THE IF

THE

THE

ASKlNG NOW?

WANT

THE

HOPE

bAY,

BUTTON THE VERY YOU FEEL YOU NEED

YOU’LL

TO

YOU.

ONE

ASK

BUT

IF

YOU

‘dE bOULD

BUT

bHAT TO DO PRESS THE THREE BUTTONS?

IT

I

YOU

REUEMBER

CAN

ANSWRS,

BUTTON NObr

‘YES’.

‘NO’*

FIND

'YES'>

YOU*

CAN

VERY

UNDERSTAND PUSH ONE OF

SIMPLE

PUSH

COMPUTER5 ARE

MARKED

MARKED

THE COMPUTER

INTERESTING

US*

DO OF

DOCTORS. ARE YOU

YOU

YOU THE

ONE

ASK SO

'NO' OR

IF

THAT

OR

DON’T

UNDERSTAND

TWO

QUESTIONS

CAN

TALK

YOU THE

EVERYTHING 0

QUESTIONS IS

ONLY

BUTTON. UNDERSTAND

BUTTONS?

THIS

ONLY QUITE

YOU

YOU

'?'

ALL

IN

ABOUT

WHY

COMPLETE

DOCTORS AND NURSES HAPPY ABOUT THIS? PUSH

0 DON’T

FEEL

THAT

INSTANT THAT TO THINK A

NEED TO READ THE QUESTION OVER TAKE YOUR TIME IF YOU YANr TO. 1 CAN’T TALK TO YOU AGAIN UNTIL THE

BUTTON

TO

‘7’

TO

PLEASE

BUTTONS? THE

YOU

THE

AS YITH JUST YOUR ANSWERS.

BY

UOULD

IF

THIS.

TALKING

EITHER

YHETHER CE

1

UNDERSTAND

TO 1

HERE.

CONFIDENCE WILL SEE ONE

AM UP

SEE

WITH

ILLNESSES.

HELPFUL

PRESS

I

TO

EXCHANGE

WITH

PUSH

UUCH.

COUPUTER

ONLY

THANKS.

YOU

VkRY

ONLY

SAID

US

PUSH THE BUTTON US. IF YOU DON’T GO AHEAD NOW AND

PUSHING

QUESTION

YOU

A

CAN BY

EXPERIMENT

HELP

VERY IT

IS

I UE

‘VE

DIAGNOSE

bOULD

GOOD.

I

AN

TO

TO

iE*LL

TO

IS TO

RATHER YOU TO ‘1’

BUT

OF THE CONVERSATIONAL

I BIT

YOU

HAVE

TO

HAVE FINISHED BEFORE YOU

PRESS TYPING. ANSWER,

OR

AGAIN THEN GO AHEAD AND DO REMEMBER, HOVEVtRe THAT YOU HAVE PUSHED ONE OF

SO.

BUTTONS.

FIRST OF ALL THEN, YELL* YOUR DOCTOR BECAUSE YOU YERE PAINS IN THE STOMACH? 0

IS ON& OF SUFFERlNG

THE REASONS YOU FROM DISCOMFORT

VISITED OR

0

178

w. I. CARDet al.

the flow diagram illustrating the logic of the interview is published elsewhere (Evans and Wilson, 1971). The standard teletype terminal presents a complex array of keys and while those with experience of computers or some typewriting skill would have no difficulty in using it, the majority of hospital patients would not be capable of operating it without assistance. A mask was therefore developed (F’ig. 1) which can be clipped over any teletype keyboard and reduces the display to three buttons labelled, YES, NO and ?.

Fig. 1.

Mask for teletype.

Patients The patients who took part were those attending the Gastrointestinal Centre, Southern General Hospital, in the ordinary way, and each was asked if he was willing to take part in this study; none refused. Each patient was interviewed either by two consultants independently or by a consultant and by the computer. The consultant interview took place in the normal way except that the proforma was completed in addition to the out-patient notes made by the consultant. If the patient were to be interviewed by the computer, he was introduced to it and the system explained to him. He was then watched to ensure that he fully understood the method of operation. After the computer interview, theproforma was completed from the computer print-out of the replies to the questions and the patient’s reactions to the method were also noted on a questionary. In all, 75 patients took part but 3 were unable to complete the interview with the computer. Since there were four consultants, counting the computer as one, there were 6 pairs with 12 possible orderings. The trial was arranged into 12 blocks of 6 patients and patients were allocated at random.

INTERROGATION

OF PATIENTS

179

RESULTS

(a) Acceptability

All patients who had been interviewed by the computer were interrogated briefly by an assistant concerning their attitude. To the question ‘Have you ever used a computer before? over 95 per cent of the patients stated they had not, while 90 per cent also answered ‘no’ to ‘Have you ever seen a computer?‘. To ‘Did you find the experiment interesting?, only one patient, who was described by the assistant as being ‘very slow and asking for help frequently’, replied in the negative. ‘Did you find it frightening or unpleasant ? elicited a 100 per cent negative response. ‘Were there any questions that you didn’t understand or found particularly difficult to answer?, produced the most variable response. Here 40 per cent of the patients indicated that they had, in fact, experienced some difficulty in the questions concerning the localisation of the pain, with a further 40 per cent commenting that they felt constrained by the Yes/No alternatives. The comment here was that a ‘Sometimes’ button would have been welcome. A few patients experienced some difficulty from particular questions which they found puzzling, e.g. uncertainty about the meaning of the word ‘vomit’. ‘Did the computer seem to be paying attention to your answers? Did you feel that there was someone actually talking to you?’ elicited a 100 per cent positive response, suggesting that the rapport we were seeking to establish between computer and patient was achieved. To question seven, ‘Would you mind if computers like this were used a lot in hospitals?, 94 per cent replied that they wouldn’t mind. A similar percentage also answered ‘no’ to question eight, ‘Do you think other people would mind?. This latter was inserted because it was felt that patients might give a ‘polite’ response to question seven while question eight would allow them to project any feeling of disquiet on to others. To the question, ‘Have you anything else that you’d like to say?‘, 85 per cent took the opportunity to make specific comments of which the majority (over 60 per cent) stated that it was ‘Very good’, ‘Very interesting’, etc. Some patients commented that it was ‘like talking to a doctor’, while about 10 per cent stated either that they felt, or thought that others might feel, that it would be preferable to a doctor. The principal reasons given were that it was ‘less embarrassing’ or that they ‘felt more free to speak’. Others commented that they felt ‘less nervous’ and two patients stated that the computer gave them ‘more time to think than the dtitor’. Others remarked on how ‘polite’ it was. A number of deaf or partially deaf patients particularly appreciated the computer’s comprehensibility. (b) Accuracy

Earlier we referred to the path between the patient’s experience of a physical event and the indicant as recorded by the doctor, as an information channel. The simplest kind of binary channel is that in which the symptom either occurs (,?I) or does not occur (E) and the resulting indicant is recorded as being present (F)

w.

180

I.

cmD et al.

or as absent (F) (Fig. 2). If the symptom occurs but is recorded as absent, this is called a false-negative error, and if the symptom does not occur but the indicant is recorded as being present, this is called a false-positive error. The probability with which the false-negative error occurs is symbolised by c1and the probability with which the false-positive error occurs is symbolised by 8. These error rates give us a measure of the accuracy of the channel.

??l

II-

F.,

Ed

.

F 0

it-

F

sgmptom PO-*)

>c

R0COldt3d preeent

8ym*m

Recorded

‘1-Q)

+ (l-P)0

F --t

Pa +(l-P)P-o)

Fig. 2. Binary channel; one consultant. a and fi are the false-negative and false-positive error probabilities. p is the probability that the sym@om is really present. E and E denote the ‘true’ presence and absence of the symptom. F and F denote the answers recorded by the consultant.

Fig. 3.

Three-dimensional

contingency

table. Explanation

in text.

INTERROGATION OF PATIENTS

181

Such a description is an oversimplication since there are at least three separate sources of error: (1) error due to a particular symptom since certain symptoms are more ‘difficult’ than others; (2) error which arises in a patient who is unobservant or inarticulate and is therefore inconsistent in his replies; and (3) error which arises from lack of skill of a doctor in eliciting information from a patient. These separate errors can be thought of as arising sequentially along the information channel. If these sources of error can be regarded as statistically independent, then the results of interrogation can be represented by a three-dimensional contingency table (Fig. 3). We can imagine a solid figure made up of cells, two cells in thickness representing a pair of consultants (j, k), 12 cells in breadth representing the set of patients (1), and 14 cells in length representing a set of 14 symptoms (i). Each cell will be occupied by a 1 or a 0 according to whether the symptom was present or absent. This three-dimensional table can be condensed into a two-dimensional table by converting the data into ‘agreements’ and ‘disagreements’. Table 3 shows the number of disagreements out of a set of 12 patients by symptom and consultant pair. TABLE3 TABLE

Symptom

1

coYtPT l&3 28~3 l&4 2&4 3&4

Total

2

OF DISAGREEMENTS

3

4

5

BY SYMPTOM

6

I

8

0 1

2 2

0 3

:.

4 3

t

24

:

: i

i i

: t

fi :

: 5

: !

2” :

:. :

9

19

18

16

23

27

12

12

AND

CONSULTANT

10

11

4 :

2 f

4 :

: 4

9 4

19

18

9

2 2

18

PAIR

12

13

14

t 1

: 2 2 :

:, 3 3 :

:1:

8

11

223

.: 3

13

Total

:: 43 39

For each symptom and consultant pair the number of disagreements (d) out of 12 is shown. Total number of consulttit-consultant disagreements = 99/504 Total number of consultant-computer disagreements = 124/504

METHOD 0~ ANALYSIS(RUSSELL)

The three possible sources of error in the communication channel can be incorporated into a model for the probabilities a and 8. The proportion of errors made by each consultant will give an estimate of that consultant’s skill in eliciting information from a patient, and the proportion of errors made for each symptom will give an estimate of the relative ‘difficulty’ of the symptoms. However, to measure these proportions it is necessary to know, for each patient and symptom, whether the symptom is actually present or absent; and usually the ‘correct’ response cannot be determined. Thus errors must be estimated indirectly, by comparing the results of the two interviews that each patient had.

w. I. CARD et al.

182

A ‘disagreement’ occurs when the two consultants interviewing a patient elicit different replies about a particular symptom. As a disagreement is due to an error in one (but not both) of the two ‘channels’ involved (each channel contains the same patient and symptom but a different consultant), estimates of the error rates can be derived from the proportions of disagreements occurrin_g (Fig. 4).

.*(l-.) .

‘“lea /”

ky

Fig. 4.

<;

__2&

Yes”-

(l-.*)

Agreement

‘Is‘

No” -

maagreement

8

‘NO

No” -

Mogr6ement

8.0 -8

‘TZO

No” -

&msment

P-8)

(1 -8’) )

(1-8.)

Binary channel; two consultants, interviewing the patient independently. Explanation as in Fig. 2.

To avoid involving the (unknown) true response, the values of c1 and /I are assumed equal for each ‘patient-symptom-consultant pair’ combination. The probability of a disagreement is then the same, whether the symptom is present or absent. This assumption is unlikely to be true in practice, but unless a and /I differ very greatly, or are very close to 0 or 1, slight deviations from the model have little effect on the probabilities. A logistic model for the probabilities ccand jI is used (Good, 1967; Cox, 1970), incorporating symptom, patient and consultant effects. From this (assuming a = /I) an expression for the probability q of a disagreement between the two consultants interrogating a patient about a symptom is derived and the proportion of disagreements between a particular consultant pair, or for a particular patient or symptom, will give information about the corresponding value of q, and therefore of a and a*. If the error probability of a consultant is always less than 0.5 then increasing his error will increase the probability of a disagreement between him and a second consultant.

INTERROGATION

183

OF PATIENTS

A linear approximation to the expression of q is sufficiently accurate for the range of probabilities occurring in the data:

loi3

qijkl 1

-

=

p

+

ki

lj +

Ak + Vjkl

12

4

ki = 0;

+

qijkl

c

lj =O; 1

c

Vjkl

=

0 for allj, k

I=1

where ki is a SymptOIn effect, Vjk[ a patient effect, and lj, &, consultant effects (j < k), for the two consultants who interviewed the patient. From estimates of these effects, the average error rates for a given patient, consultant, or symptom can be estimated. As for each value of (i, j, k, l), i.e. for each ‘patient-symptomconsultant pair’ combination, there is only one binary observation (‘agree’ or ‘disagree’), this model must be simplified so that the probability qijkl can be estimated. Symptom effects can be ignored (ki assumed zero), when, for each patient, the number of disagreements out of 14 is used; and least squares estimates of consultant effects obtained. These agree well with the results finally used, but give no estimates of the comparative difficulty of eliciting different symptoms. If patient effects (Vjkl)are ignored, then, for each symptom and consultant pair, there are 12 patients with the same probability of disagreement (see Table 3), The proportion of these patients who give a disagreement for this symptom will give atI &iIIlate &ijk Of the r&VaIlt qijk,so that least squares estimates of p, ki, lj, can be found, the existence and the size of symptom and consultant effects tested, and the probabilities of errors for different symptoms and consultants obtained. This can be done assuming constant variance or using an empirical weighting. Although with larger samples the latter would be better, it is less likely to be accurate for this particular experiment, so the conclusions are based on the unweighted analysis.

RESULTS OF ANALYSIS

There appears to be no significant difference in the error probabilities between the three human consultants (Table 4). The computer is significantly less accurate (significance level 3 per cent) than the consultants. In comparing the computer with the other consultants, a one-sided test has been used, between ‘computer as good as or better than consultants’ and ‘computer worse than consultants’, the latter being the conclusion arrived at.

184

W. I. CARD

et al.

TABLE 4 ESTIMATED ERROR PROBABILITIES OF CONSULTANTS AND SYMPTOMS

(a) Consultants Consultant Consultant Consultant Consultant The standard errors of these estimates are the largest standard error. (b) Symptom

1: O-086 2: o-125 3: 0.095 4: O-185 (computer) between (approx.) 0.02 and @03, the computer having

1: 0.070 2: O-162 3: O-132 4: 0.136 5: 0.173 6: 0.209 7: 0080 8: 0099 9: o-160 10: O-155 11: 0.154 12: o-093 13: 0.075 14: 0.084 The standard errors of these estimates are considerably so these estimates are of limited value.

larger than those for consultant

effects,

(b) Symptoms

The overall effect of’symptoms on the probability of error is not significant (level 30 per cent), but symptom No. 6, post-cibal nausea, was thought likely to produce error and this is confirmed by the data. (c) Order effect

The model used has no order effect, but the possible existence of one can be tested independently. Two such effects appear possible: (i) The patient may pay less attention in the second interview (especially with the computer), and therefore make more errors. Thus a disagreement between computer and consultant would be most likely when the computer was used for the second interview. (ii) The patient may tend to give the same answer in the second interview as he gave in the first, whether the first answer was true or false (reinforcement). The effect of this is in the opposite direction to that of(i). When the data are compared with the distribution when no order effect is present, the effect is in the direction of(i), although there is no significant evidence that the accuracy of the computer is different at first and second interviews. The methods of analysis used here are not the only possible ones: other transformations of the binomial results could be used, or distributions conditional on question totals could be analysed. As there are only 2.7 disagreements out of’12 for a ‘symptom-consultant pair’, the normal approximations used in the analysis are not completely justified.

,

INTERROGATION

OF PATIENTS

185

DISCUSSION

(a) Acceptability

Interrogation through a computer program has been tried for some years and patients have been prepared to accept the method and have even welcomed it (Slack and van Cura, 1968). The results of this present study suggest an acceptable and effective method of interaction between a naive user and a computer could be developed. Acceptability may be due to one or more of the following: (1) Patients spontaneously commented on the comprehensibility of the questions. The teletype prints at a leisurely 10 characters per second and even slow-reading patients have ample opportunity to consider the question and even to read it a second or third time if they wish. (2) The computer terminal presents a classless, impersonal face which, judging by comments after the experiment, overcomes some of the barriers that may still exist between the doctor and his ‘working-class’ patients. (3) The computer also presents a ‘non-judging’ face to the user. Patients traditionally look for signs of approval or disapproval of their answers to the physician’s questions and may even modify their responses to some extent, to avoid his displeasure. (4) The patient can take the interview at his own pace as the computer will wait more or less indefinitely for his answer and this induces an unstressful atmosphere. However, if computer interrogation is ever to become completely acceptable it would be desirable to introduce methods for adapting the style of interrogation to a particular patient, just as a doctor does. For example, the speed of interrogation might be linked to the patient’s response times. Additional information would be gained if the keyboard were designed so that the patient could qualify his reply. (b) Accuracy

Most authors who have used a questionary or .who have explored computer interrogation have used a fixed set of questions. Unfortunately, a single set of questions, at any rate in Britain, can mean different things in different parts of the country. We therefore believe it is wiser first to define the symptom in strictly medical terms and then frame the set of questions necessary to elicit it. These can then take into account regional differences of language. The representation as an information channel, of the path between the patient’s experience of an event and the recorded indicant, seems plausible and allows us to attempt measurement of error rates of the channel. Other authors have compared the response to interrogation by computer or by self-administered questionary with the response to questioning by the doctor (Slack et al., 1966; Mayne, 1970; Simmons and Miller, 1970; Mellner, 1970), or have retested the patient using the same questions (Collen et al., 1969). Unless some model is devised which allows

W. I. CARD et al.

186

rates of error to be estimated such studies only measure imprecision and do not measure accuracy. In this study, interrogation by the computer, while roughly comparable to interrogation by a doctor, was significantly less accurate. The comparison made is a stringent one since it is the consultant who framed the questions for the computer program and who, when interviewing the patient, was free to ask as many further questions as he liked, while, from the attitude and tone of voice of the patient, he could gain information that was denied to the computer. It is therefore not easy to see how computer interrogation can be more accurate than a specialist in his own field &eliciting evidence though it might be more accurate than a non-specialist. Increased accuracy is not, however, an end in itself but is the.means whereby the evidence contributed by an indicant is strengthened. This in its turn may affect a decision on management. Since all decisions are influenced by costs, buying cheaper but less accurate evidence might be preferable to evidence that is more accurate but more expensive. Interrogation by computer is not therefore excluded because it may prove less accurate. A true comparison of different methods of interrogating patients is more complex than appears at first sight.

ACKNOWLEDGEMENT

We are grateful to Professor R. L. Plackett for statistical advice.

REFERENCES ABRAMSON, N., Information theory and coding (1963) McGraw-Hill, London. CARD, W. I., and Goon, I. J., A logical analysis o! medicine, In Companion to medical studies

Vol. 3, (Eds.) R. Passmore and J. S. Robson (1974), Blackwells, Oxford.

CQLLEN,M. F., CUTLER? J. L., SIEGELAUB, A. E., and CELLA, R. L., Rehabdrty of a self-administered medical questionnaire, Archives internal Medicine, 123 (1969) p. 664.

Cox, D. R., Analysis ofbinury data (1970) Methuen, London. to allow computer based history-taking in cases of suspected gastric ulcer, National Physical Laboratory Report, Computer Science, No. 49, 1971. Goon, I. J., Contribution to the discussion of a paper by S. F. Buck and A. J. Wicken, Journal Royal Statistical Society, Series C, 16 (1967) p. 206. GOOD, I. J., and CARD, W. I., The diagnostic process with special reference to errors, Methods of information in medicine, 10 (1971) p. 176. GREW, N., Cosmologiu Sucru (1701). Rogers, Smith and Walford, London, p. 66. KANNER, I. F., Programmed medical history-taking with or without computer, Journal American Medical Association, 207 (1969) p. 317. MAYNE, J. G., Clinical data acquisition, In Information processing of medical records, Eds. J. Anderson and J. M. Forsythe (1970), North Holland, Amsterdam.

EVANS, C. R., and WILSON,JACKIE,A program

MAYNE, J. G., WEIUEL W. and SHOLTZ P. N., Towards automating the medical history, Mayo

Clinic Proceedings, 43 (1968) p. 1. MELL,~l~7b,The self-admmtstered medical history, Actu Chirurgica Scandinavicu, Supplement, RUSSELL,D., 1; preparation.

INTERROOATION OF PATIENT!3

187

BMMCI~, E. M., and MILLER,0. W., A new concept in automated patient histories, In Information processing of medical records, Ed. J. Anderson and J. M. Forsythe (1970), North Holland, Amsterdam. medical SLACK, W. V., HICKS, G. P., REED, C. E., and CURA, L. J. van, A computer-based history system, New England Journal of Medicine, 274 (1966) p. 194. SLACK,W. V., and SLACK, C. W., Good questions and bad, In Information processing of medical records, Ed. J. Anderson and J. M. Forsythe (1970), North Holland, Amsterdam. SLACK, W. V., and CURA, L. J. VAN, Patient reaction to computer-based medical interviewing, Computers and Biomedical Research, 1 (1968) p. 527,