able by a typical observer. b. The observer level, at which a typical observer read- ing the test experiences a net gain in information, or reduction in uncertainty. c, The diagnostic level, at which the information pro- vided by the test influences the diagnosis. d. The management level, at which the test result in- fluences management or treatment. e. The outcome level, at which the u l t imate outcome experienced by the pat ient was affected by the test re- sult. f. The societal level, at which the difference between society 's net benefits and ne t costs is posi t ively af- fected by the test result.

Thus, a test that fails to affect management may in fact be useful in confirming or ruling out a previously suspected diagnosis, or conversely, a test result that does change patient management may still not affect pat ient outcome.

2. When es t imat ing potent ia l savings, the authors uni- formly failed to distinguish between charges and costs. This can result in gross overestimates of the savings to be real- ized. A significant change in the ut i l izat ion rate of a test will result in fixed costs (such as amort izat ion of radiograph machines, mul t ichannel analyzers, etc) being shifted to the remaining patients; thus only the variable costs of a test (eg, the materials used, and to a l imited extent, labor costs) wil l be saved, z

3. It was surprising that no ment ion was made of the use of the receiver operating characteristic (ROC} curve 3 to eval- uate a test 's efficacy. ROC curve analysis has many advan- tages over other techniques and has vir tual ly become the standard for evaluating imaging modalit ies, al though it can be applied to a test of any sort.

4. The efficacy of a test is affected by the choice of a posi t ivi ty criterion. The authors did not address the ques- t ion of whether or not a change in the posi t ivi ty criterion for a given test might be more useful than abandoning a test.

In addition, it has been shown that the arbitrary division of test results into dichotomous, positive or negative, ranges loses some of the information that the test provides, and that use of continuous scales or one or more intermediate ranges for results is associated with an increase in informa- tion content. 4

5. Finally, there is a hidden reductionist bias in the study of medical decision making by examina t ion of i ts indi- vidual components. To the extent that diagnosis is a pat tern r ecogn i t ion task, i t is no t l i ke ly tha t r e duc t i o n i s t ap- proaches to understanding will be very productive. For ex- ample, what criteria does one use to recognize the letter A? Studies of pa t tern-recogni t ion and typeface design 5 have produced the remarkable idea that 'A-ness" cannot be bro- ken down into components that can be expl ic i t ly tested wi thout substantial loss of accuracy.

While a reductionist approach is often extremely power- ful, it is somet imes analagous to the story of the defense a t torney in a murder case in which the v ic t im died of 10,000 separate pinpricks. Since any single pinprick could not be identified as the cause of death, his conclusion was that the death could not have been caused by the pinpricks. Further s tudies of test ing for diagnosis and managemen t should be carried out wi th these considerations in mind.

Robert L Wears, MD, PA Orange Park, Florida

1. Fryback DG: A conceptual modelfor output measures in cost-effective- ness evaluation of diagnostic imaging. J Neuroradiology 1983;10:94-96. 2. Weinstein MC, Fineberg HV, Elstein AS, et aI: Clinical Decision Analy- sis. Philadelphia, WB Saunders, 1980, p 241. 3. Swets JA, Pickett RM: Evaluation of Diagnostic Systems: Methods From Signal Detection Theory. New York, Academic Press, 1982. 4. Rifkin RD: Maximum Shannon information content of diagnostic medi- cal testing: Including application to multiple non-independent tests. Med Decis Making I985;5:I79-190. 5. Hofstadter DR: Metamagical Themas. New York, Basic Books, 1985, pp 243, 260-296.

Do Patients Who Leave Without Being Seen

To the Editor: I enjoyed reading the article "Patients Who Leave With-

out Being Seen" by Weissberg et al [July 1986;15:813-817]. Their conclusion that mos t pat ients who leave wi thou t being seen (LWBS) have significant psychological and/or so- cial problems is interesting, especially in view of the l im- ited number of published reports on this group of patients.

I mus t take exception to their s ta tement that "most pa- tients who leave prematurely give ample warning." This is contrary to the experience at m y hospital, where the patient rarely makes any sort of s ta tement of in tent ion to leave, but more l ikely s imply fails to respond when called into our examin ing room or jus t "d isappears" af ter hav ing been placed in a room. This is also contrary to the few published reports. Wartman et al 1 profile the LWBS pat ient as "a per- son who lives wi th in 2V2 miles of the hospital, has Medi-

Give Warning?

care/caid or no medical insurance, has no private physician and has a non-serious complaint ." In m y opinion, it would be difficult to use these data to prospectively identify poten- tial leavers wi th any certainty. Gibson et all 2 in a study of patients who LWBS, concluded "patients who are l ikely to leave the emergency depar tment prematurely probably can- not be accurately identified on initial presentation." Finally, in Weissberg's own paper, the only differentiat ing demo- graphic factors were that patients who LWBS were less like- ly to be married and less l ikely to have a telephone.

Assuming that the patient who is l ikely to LWBS can be identified early (by demographics or by an actual s ta tement of intent to leave), the suggestion that "his status should be re-assessed and the patient seen as soon as possible" is prob- lematic . Presumably the pa t ien t has already been triaged

16:4 April 1987 Annals of Emergency Medicine 474/147

CORRESPONDENCE

and is waiting because of a nonurgent presenting complaint. Implicit in this is that patients with more urgent com- plaints are being seen and treated. It is at least debatable whether the patient with psychosocial problems (ie, new person in home, money problems, alcoholism, assault, etc) and a nonurgent compla in t should be triaged as more urgent than the patient with the same nonurgent complaint and no psychosocial problems. Hopefully, the patient with significant depression, suicidal intent, or violent behavior has been identified and triaged to a more urgent category on initial presentation.

Matt Gratton, MD Department of Emergency Health Services University of Missouri-Kansas City

School of Medicine 1. Wartman SA: Emergency room leavers: A demographic and interview profile. J Comm Health 1984;9:261-268. •

2. Gibson G, Maimon LA, Chase AM: Walkout pat ients in the hospital emergency department. JACEP 1978;7:47-50.

In Reply: We appreciate the opportunity to review Dr Gratton's

thoughtful comments. As he indicates, no data exist now to predict the patient who will leave without being seen. No demographic, clinical, or "vital sign" features appear to sep- arate LWBS patients from those who choose to stay for care. However, it is our experience that many LWBS patients do announce their departure in advance - - they complain,

threaten, or otherwise signal their intent to leave. Unfortu- nately we did not document that feature of LWBS behavior in our study.

We disagree with Dr Gratton's last statement that "hope- fully, the patient with significant depression, suicidal intent or violent behavior has been identified and triaged to a more urgent category on initial presentation." Unfortunately, this is not always so. Several studies have shown that a high proportion of patients with psychosocial stress, serious de- pression, suicidal intent, or other violent behaviors are missed during physician encountersJ -3 If further studies confirm that patients who intend to LWBS are at high risk for violent behavior, then such patients should be given a higher triage rating; no matter how trivial their initial phys- ical complaint, these patients would represent true life- and limb-threatening emergencies.

Michael P Weissberg, MD Department of Psychiatry Steven R Lowenstein, MD, MPH, FACP Departments of Medicine and Surgery University of Colorado

Health Sciences Center Denver, Colorado I. Weissberg MP: Dangerous Secrets. New York, WW Norton, 1983, p 26-28. 2. Weissberg MP: The somatic complaint: A ticket of admission for child abusers. Primary Care 1977;4:283-289. 3. Murphy GE: The physicians responsibility for suicide, I and II. Ann In- tern Med 1975;82:301-309.

Physician's Immunity in Child Abuse Reporting

To the Editor: In the first challenge of the 1980 Child Abuse Reporting

Law, the California Court of Appeal ruled that physicians are absolutely immune from any civil liability for reporting a case of suspected child abuse to a child protective agency [Storch v Silverman, B-015977 Oct 21, 1986]. This immuni ty was found to be absolute even if the child abuse report turns to be false or unsubstantiated. This decision should remove any remaining hesitancy about child abuse report- ing among medical professionals in California based on the fear of liability.

This appellate court decision is significant because had they found the opposite, the medical profession would have been caught in a seriously conflictual situation. If the physi-

cian did not report, the physician would be subject to pros- ecution; if the physician did report, he would likewise be subject to further liability.

The emergency physician is morally obligated to report child abuse, as he may be the child's only spokesman. Now physicians in California can report what they feel is the truth without the fear of reprisal.

Jonathan Wasserberger, MD, FACEP Gary J Ordog, MD, FACEP Martin Luther King Jr General Hospital Karen J Travis, JD Los Angeles, California

Aortoenteric Fistula

To the Editor: I read with interest the article 'Aortoenteric Fistula: A

Catastrophe Waiting to Happen" by Grigsby, Eitzen, and Boyle [June 1986;15:731-734]. There are several points in their article I would like to discuss.

The authors state that their patient had endoscopic gas- troduodenoscopy performed twice. No ment ion is made whether endoscopy visualized the third portion of the duo-

denum. When the diagnosis of aortoenteric (A-E) fistula is entertained, endoscopy is not valid unless the third portion of the duodenum is visualized, as this is the site where 75% of A-E fistulas occurJ It also must be emphasized that the diagnosis of A-E fistula by endoscopy is extremely poor, with sensitivities of 38% and 0% as reported in the studies of Perdue and Flye, respectively.Z, 3

The authors seem to de-emphasize the importance of an- cillary diagnostic studies in the diagnosis of A-E fistulas by

148/475 Annals of Emergency Medicine 16:4 April 1987