Psychosomatics 49:104-108, March-April
doi: 10.1176/appi.psy.49.2.104
© 2008 Academy of Psychosomatic Medicine
Misdiagnosed Delirium in Patient Referrals to a University-Based Hospital Psychiatry Department
Susan E. Swigart, M.D.,
Yasuhiro Kishi, M.D.,
Steven Thurber, Ph.D.,
Roger G. Kathol, M.D., and
William H. Meller, M.D.
Received July 14, 2006; revised December 12, 2006; accepted January 4, 2007. From the Dept. of Psychiatry, Univ. of Minnesota; Dept. of Psychiatry, Tokai Univ.; Dept. of Psychology, Woodland Centers Consultation–Liaison Service. Send correspondence and reprint requests to Dept. of Psychology, Woodland Centers, 1125 SE Sixth St., Willmar, MN 56201. e-mail: steven_thurber{at}yahoo.com
© 2008 The Academy of Psychosomatic Medicine
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ABSTRACT
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The authors examined the factors associated with referral errors in which the presence of delirium was ostensibly not recognized by medical staff personnel. Medical records of 541 university-hospital patients consecutively referred for psychiatric consultation were scrutinized for extant delirium. The data indicated that a greater likelihood of a missed diagnosis was associated with younger age; referrals outside of family practice service; orientation as to person, place, and time; and a history of bipolar affective disorder or psychosis. The ramifications of failure to diagnose existing delirium include increased morbidity and mortality, longer length of hospital stay, and increased healthcare costs.
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INTRODUCTION
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Delirium is a disorder of brain functioning that involves a disturbance of consciousness, with reduced capacity to focus or sustain attention. It represents a change in cognition that is characterized by disorientation and memory or language disturbance. It is usually transient in nature and typically develops over hours-to-days.1 Risk factors for delirium include severity of illness, older age, and baseline dementia.2–5 Among multitudinous causes of delirium are medication, infection, trauma, and metabolic and cardiovascular disturbances.6
Delirium is a common disorder in medical and surgical inpatients. An estimated 10%–41% of inpatients have delirium during their hospital stay.7–10 Rates increase in acutely ill geriatric populations. Depending on the study, anywhere from 10% to 56% of these patients develop delirium during their hospitalization.2–4 The highest rate (61%) was reported by Gustafson for elderly patients who received surgery for femoral neck fracture.1
Although delirium is a common disorder, it is frequently not recognized by treating physicians and nursing staff. It has been demonstrated that physicians only document symptoms and signs of delirium in 30%–50% of affected patients.4 A study by Armstrong et al.4 found that 46% of patients with delirium were misdiagnosed by the referring service personnel. Also, the authors reported that house staff persons on the general-medical wards made fewer diagnostic errors than those on surgical wards. Symptoms of delirium may be mistaken for symptoms of depression. Nicholas and Lindsey11 reported an error rate of approximately 6% in this regard. Other investigators have found much higher diagnostic error rates. Margolis12 indicated that 37% of patients referred to the psychiatry consultation service for depression were, instead, found to have delirium. Farell and Ganzini’s data7 conflate with those of Margolis; 42% of patients referred for depression actually showed symptoms of delirium. Again, it was reported that house staff members on the general-medical wards were more accurate than surgical staff persons in relation to delirium diagnoses.12 Correspondingly, Berkowitz13and Agbayewa14 reported that medical and surgical staff persons had poor knowledge about organic brain syndromes, with surgeons ranking lower that other medical staff members in this regard.
Failure to diagnose delirium may have many adverse sequelae, including morbidity, mortality, longer hospital stays, and increased healthcare costs.14–17 Furthermore, patients with accurate delirium diagnoses have a two- to twenty-fold increase in hospital mortality.2 They also have longer hospital stays and increased risk for institutionalization. In 1999, Inoye reported that delirium involved more than 17.5 million inpatient days and accounted for more than $4 billion of Medicare expenditures. Additional costs result from increased rates of institutionalization, rehabilitation, and home care.16
Mortality rates for patients with delirium have been reported to be between 10% and 65%.3 Weddington found that up to 25% of patients with delirium die within 6 months of discharge from the hospital.17 Francis and Kapoor2,18 reported increased 2-year mortality, increased loss of independent living, and decreased cognitive performance in elderly patients with delirium.
Our experiences in the psychiatry consultation–liaison service included referrals of general-medical patients for psychiatric concerns who clearly had delirium. This engendered an interest regarding factors that may preclude nonpsychiatric medical staff persons from recognizing delirium symptoms. We therefore began an investigation of patient and physician variables that are associated with misdiagnoses, with particular reference to the past psychiatric history of patients. The current study has a larger sample size than the earlier investigation of Margolis12 (N=48), and differs in that our objective was specifically related to misdiagnosed delirium (Margolis focused on degree of congruence between each house staff diagnosis and the corresponding psychiatric diagnostic classification). Farrell and Ganzini’s7 data were gathered on misdiagnosed delirium involving 67 persons age 60 and over who were referred explicitly for treatment of depression. Our study extends research on misdiagnosed delirium to a larger, more heterogeneous sample vis-à-vis age, psychiatric history, and referral questions.
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METHOD
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The participants were consecutive referrals for psychiatric consultation at Fairview University Medical Center, associated with the University of Minnesota. These patients were referred between January 1, 2001 and December 31, 2001. The hospital is a public university hospital located in the 15th-largest metropolitan area of the United States. Approximately 15% of persons in the catchment area are non-Caucasian. During the 1-year investigation, there were 17,629 admissions to the general hospital wards; 541 patients (3.1%) were evaluated by the psychiatric consultation team, which consisted of an attending psychiatrist, psychiatry residents, and medical and pharmacy students. Records of any past psychiatric treatment were reviewed, and each referred patient received a diagnostic interview by a member of the consultation team. Delirium was diagnosed with reference to the criteria of DSM–IV. Several different team psychiatrists provided diagnoses, a weakness in the study noted below. The following information was recorded for each referred patient: patient demographics, dates of admission and discharge, requesting service, reason for referral, consultation diagnosis, and recommendations. The study was approved by the Institutional Review Board at the University of Minnesota.
The referred patients diagnosed with delirium by the psychiatric consultation team were divided into "accurate" versus "misdiagnosed" classifications. Misdiagnosis was defined as a diagnostic discrepancy in which a patient who met DSM–IV criteria for delirium received a different classification by the referring physician. Mean-difference t-tests and Pearson chi-square statistics were then computed for demographic factors, previous psychiatric diagnoses, current number and types of medication, and inferences made by referring physicians regarding mental status. For data with small cell counts, we used Fisher’s exact test. Variables that differentiated the two groups at a p value of <0.10 were then included in a forced-entry logistic-regression analysis.
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RESULTS
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Among 541 patients who received psychiatric consultation (one consultation per patient), 525 records were available. Of this number, 100 were diagnosed as having delirium. The mean age of these patients was 56.51 years. Fifty-five percent were male, and almost 80% were Caucasian; only 20% of delirium patients were employed; 71% of these patients had some type of past psychiatric history: almost 38% had a history of depression; 20% had previous diagnoses of substance-use disorders; and 18% were found to have a history of psychosis or bipolar disorder (Table 1).
Referring services included Medicine (37%), Surgery (26%), Family Practice (23%), ICU (10%), and 4% "other." Among the 100 delirium patients, reasons for referral were available for 99; 36 were correctly referred for psychiatric consultation for "delirium/confusion;" 63 patients were misclassified and referred for reasons other than "delirium/confusion:" depression (33%), chemical-dependency evaluation (22%), general psychiatric evaluation (17.5%), suicidal ideation (14%), psychosis (8%), anxiety (5%), agitation (5%), competency evaluation (5%), behavior problems (3%), and somatization (1.6%).
With reference to Table 2 and Table 3, younger patients with delirium were more likely to be misdiagnosed (p=0.004). Consistent with data discussed above, there was a trend for the family practice service personnel to be more accurate than other medical services (p=0.072). Although the presence of a previous psychiatric history was not a distinguishing variable, the nature of the previous diagnosis was statistically reliable: patients with a history of bipolar disorder or psychosis were much more likely to be misdiagnosed (p=0.02). Finally, patients who were found by referring personnel to be oriented as to person, place, and time were likely to be misclassified (p<0.05). Length of hospital stay, gender, marital status, race, and employment status were not differentiating variables. When the significant distinguishing variables were combined in logistic regression, the odds of a missed diagnosis were nine times greater when there was a history of psychosis or bipolar disorder (controlling for the other independent variables) and approximately four times greater when there was a finding of adequate orientation. A misdiagnosed referral was three to four times less likely if initiated by a family practitioner (Table 4).
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DISCUSSION
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The findings of this study suggest several variables that may preclude accurate diagnoses of delirium by referring personnel. Younger patients with delirium may be missed because the dysfunction is not perceived to be as prevalent a condition in younger patients. We may also infer that too much subjective weight is given to the absence of disorientation in eliminating delirium as a diagnostic possibility; referring personnel may not investigate possible extant mild delirium in such instances.
It can also be posited that the amount of time allotted to patients may increase the likelihood of an accurate referral diagnosis. Although it is not known whether family practitioners actually spend more time with their patients, this is a hypothesis that might be investigated in future studies of this type. It is possible, for example, that subtle memory deficits associated with mild delirium may not be ascertained if interactions are brief and relatively superficial. Our data also suggest that a patient’s erratic behavior, often a sign of delirium, may be misattributed to past psychiatric conditions, thus precluding consideration of a delirium classification. In any event, of 17 patients with a history of bipolar disorder or psychosis, only 2 were correctly diagnosed with delirium. It should be noted that, contrary to our results, an earlier study, by Farrell and Ganzini,7 found diagnostic confusion, and, hence, misdiagnoses, related to overlap between symptoms of depression and delirium (e.g., dysphoria), as well as factors involved in aging (functional impairments). As mentioned above, such discrepancies may be explained in part by a larger and more heterogeneous sample in the current investigation.
This study has several methodological limitations. The study is a retrospective analysis of consultation records. Standardized psychiatric scales and structured clinical interviews were not used. Different psychiatric consultants provided services, and reliability of the delirium diagnoses was not measured. It is also possible that in consultation referrals for chemical dependency, referring clinicians actually perceived delirium (and hence were not in error) but viewed the symptoms as ephemeral, in relation to intoxication and withdrawal. Also, the findings obtained in this study may not generalize to other psychiatric consultation–liaison services dealing with patients with more severe or unusual disorders.
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CONCLUSIONS
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The current investigation extends previous research relative to the nature of the research questions addressed and includes a larger, more heterogeneous group of participants. Medical personnel who refer patients for psychiatric consultation may fail to diagnose delirium in patients with a history of severe psychiatric illnesses. Also, the absence of disorientation in patients may dominate perceptions such that possible delirium is not fully investigated. Preconceptions of delirium as indigenous to older persons may also be associated with misdiagnoses. Family practice physicians were found to be more accurate in diagnosing delirium than other medical specialists; the hypothesis that such physicians may spend more time with referred patients was suggested.
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REFERENCES
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- Gustafson Y, Beggren D, Brannstrom B: Acute confusional states in elderly patients treated for femoral neck fracture. J Am Geriatr Soc 1988; 36:525–530[Medline]
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ABSTRACT
INTRODUCTION
