Original Research

Dementia: Predictors of diagnostic accuracy and the contribution of diagnostic recommendations

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  • OBJECTIVES: To explore and quantify the relative contribution of guideline recommendations and other determinants in the family physician’s diagnostic work-up of patients suspected of dementia.
  • STUDY DESIGN: We prospectively studied 64 family physicians in an Eastern district in the Netherlands who diagnosed dementia according to the national Dutch guidelines in primary care. Their diagnoses were compared with the reference standard embodied by the memory clinic team of the University Medical Center Nijmegen.
  • POPULATION: The physicians evaluated 107 patients older than 55 years suspected of having dementia.
  • OUTCOMES MEASURED: Predictive value of various clinical and demographic parameters were measured in both univariate and multivariate logistic regression analyses.
  • RESULTS: Activities of daily living (ADL) dependency (odds ratio [OR] = 5.3, P = .03), years since symptoms first started (OR = 1.84, P = .03), and the presence of somatic comorbidity (OR = 0.48, P = .02) independently contributed to the prediction of the presence or absence of dementia. The area under the receiver-operating characteristic (ROC) curve for these 3 variables together was 0.79. The ROC area of the family physicians’ diagnosis to determine the final diagnosis was 0.74. The number of recommendations applied did not additionally contribute to the assessment of the final diagnosis.
  • CONCLUSIONS: The diagnostic accuracy of the family physician was reasonable. For family physicians, ADL dependency is a better predictor of dementia than cognitive impairment. Family physicians should be aware of diagnostic difficulties in patients with somatic comorbidity. We were unable to confirm the diagnostic value of many of the recommendations of dementia guidelines.


 

References

KEY POINTS FOR CLINICIANS
  • Activities of daily living dependency and a longer time since the onset of symptoms are associated with a diagnosis of dementia, whereas somatic comorbidity is associated with the absence of dementia.
  • Family physicians should be aware of diagnostic difficulties in patients with somatic comorbidity.
  • We were unable to confirm the diagnostic value of the recommended dementia guidelines.
Family physicians are commonly the first health care workers to have contact with elderly individuals suspected of having dementia, and are often the only physicians involved in diagnosing the condition. Earlier studies reported poor detection and moderate recognition of dementia by family physicians.1-3 Some authors argued that family physicians should therefore refer all suspected patients for specialist assessment.4 However, family physicians must first make an accurate patient selection. Now that dementia guidelines for primary care are widely available, determining whether their recommendations contribute to diagnostic accuracy would be valuable.5-7

Some authors have hypothesized that the continuity of care typical of family practice is an important tool for family physicians to recognize cognitive and behavioral changes in their patients.8 The finding of a positive association between the number of previous contacts with the patient and the family physician’s diagnostic accuracy supports this assertion.1 The family physicians’ accuracy is also positively associated with the severity of the dementia.1,3,9 However, 2 intervention studies that tried to improve the family physicians’ diagnostic accuracy were inconclusive.10,11 Although family physicians may be hesitant to communicate a diagnosis of dementia to patients and their relatives,12 an early and accurate diagnosis is important for a number of reasons. First, explaining the diagnosis enables the patient and relatives to better understand and deal with changed behavior.13,14 Second, realizing the progressive nature of the condition permits patients and relatives to prepare for future care planning and allows support for the often severely burdened caregivers.15,16 Third, dementia patients with Alzheimer’s disease may benefit from anti-Alzheimer drugs.17,18 Therefore, the aim of this study was to quantify the relative contribution of guideline recommendations and other diagnostic determinants in the family physicians’ work-up of patients suspected of having dementia.

Method

Subjects and design

All 250 family physicians from an eastern district in the Netherlands (Nijmegen) were approached by mail to participate in a prospective dementia case-finding study. Of these, 64 family physicians participated. The main reasons for not participating were limited time, having a young practice population, or having no interest in the subject. During consultations or home visits the family physicians assessed patients newly suspected of having dementia using the dementia guideline of the Dutch College of General Practice (DCGP).5,19 Suspicion of dementia was defined by 2 criteria: age 55 years or older and presence of signs of cognitive impairment that had not yet been evaluated. These signs included memory complaints, worsening orientation, or behavioral changes and could be reported by patients or family members or observed by the family physician. After the family physicians’ assessment using the Dutch guideline, all patients with suspected dementia were referred to the outpatient memory clinic of the Academic Medical Center of Nijmegen. Their evaluation served as the diagnostic reference standard. The Medical Ethics Committee of the University Medical Center St Radboud in Nijmegen approved of the study and informed consent of patients was sought by the family physician. A few patients were not able to reproduce basic information about the study, in which case informed consent was sought from their principal caregiver.

Dementia guideline

The DCGP dementia guideline is a national, evidence-based guideline for the diagnosis of dementia (Table 1). It contains diagnostic criteria of the Diagnostic Statistical Manual, 3rd edition, revised (DSM-III-R)20 and includes assessment of cognitive, physical, and activities of daily living (ADL) functioning. A cognitive screening test such as the Mini-Mental State Examination (MMSE) is optional. Instead, the dementia guideline includes a brief assessment of 11 cognitive functions that correspond to the DSM-III-R criteria (long- and short-term memory; orientation to time, place, and person; gnosis; praxis; language ability; judgment; personality changes; and abstraction), and indications on how to assess these functions. In Table 1 the recommendations of the DCGP guideline are compared with the dementia guideline of the Veterans Affairs (VA) and of the Agency for Health Care Policy and Research (AHCPR). These 2 guidelines are constructed for use in primary care as well. The DCGP guideline closely resembles the VA and AHCPR guidelines with some exceptions.21 Results about the applicability of the Dutch dementia guideline to practice were recently published.22

TABLE 1

Comparison of recommendations in 3 dementia guidelines

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