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

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Original Research

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

J Fam Pract. 2002 August;51(8):693-699

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References

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Results

Patients and family physicians

Over 16 months, 64 family physicians enrolled 107 patients suspected of having dementia, a mean of 1.7 patients per family physician. The participating family physicians were aged an average of 47 (SD = 7) years old and handling a practice population of 2113 (SD = 600) patients. Their characteristics were comparable to other Dutch family physicians except that they included fewer solo practitioners (32% versus 49% nationwide) and slightly more female family physicians (21% females versus 17% nationwide).³⁴ Both the family physicians and the memory clinic completed the diagnostic evaluation for 93 patients: 14 patients dropped out because of refusal (n = 9), medical complications (n = 3), or death (n = 2). The clinical and demographic characteristics of these 14 patients were comparable to those of the 93 completed patients. Of the 93 patients, 93% lived independently and 62% were married. Other demographic characteristics are shown in Table 4. For 22 patients no informant was available (23.6%). The available informants were partners (77%), children or stepchildren (19%), or friends, neighbors, and others (4%). Of the informants, 67% were female and 66% shared a household with the patient.

A mean of 26 of the 31 recommendations (84%) was applied for each patient (SD = 3.3; range, 15–30). The family physicians needed on average 3.6 (SD = 3.3) contacts to assess a patient, and 40% received a home visit. Most patients were well known to the family physician; only 18% were not at all or only somewhat familiar. The MMSE was used as a diagnostic tool for only 19%. The mean time between the last assessment contact of the patient with the family physician and the first visit at the memory clinic was 61 days (SD = 39). The mean duration of the symptoms before the assessment was 22 months (SD = 13).

Diagnostic accuracy

Table 3 shows the accuracy of the family physicians’ and the DSM-III-R diagnoses compared with the memory clinic diagnoses. The prior probability of dementia was 63.4% (59/93). A positive diagnosis by the family physician increased the probability (positive predictive value) to 80.3%, and a negative diagnosis decreased this probability to 31.2% (10/32). The positive and negative predictive values of the DSM-III-R criteria were much lower (Table 2).

The 9 patients classified unsure by the family physicians were diagnosed by the memory clinic team as having amnestic syndrome (n = 3), dementia (n = 2), delirium (n = 1), age-dependent cognitive decline (n = 1), depression (n = 1), and unavailable (n = 1). Of the 12 patients with a false-positive diagnosis, 6 showed cognitive impairment, but did not fulfill all diagnostic criteria of dementia, and 1 patient received a diagnosis of depression. Of the 8 patients with false-negative findings, 6 had Alzheimer’s disease, 1 had dementia with unknown cause, and 1 had a normal pressure hydrocephalus. The family physicians expressed diagnostic confidence in 59% of all cases and in 47% of the patients diagnosed with Alzheimer’s disease.

Classification of the 8 patients labeled “unsure” as “dementia present” or “dementia not present” led to only small differences in the positive and negative predictive values (Table 2).

TABLE 2

Dementia diagnoses of family physicians and DSM-III-R compared with the memory clinic team (reference test)

	Reference test
	Dementia (n = 59)	No dementia (n = 34)	Total	PPV	NPV	SE	SP	LR+	LR–
Family physician diagnosis
Dementia	49	12	61	0.80*	0.69*	0.85*	0.65*	2.43*	0.23
Unsure	2	6	8
No dementia	8	16	24	0.74^†	0.66^†	0.86^†	0.47^†	1.62^†	0.30^†
DSM-III-R criteria^‡
Dementia	13	8	21	0.62	0.36	0.22	0.76	0.92	1.03
No dementia	46	26	72
*Dichotomizing the family physicians’ diagnoses by grouping the unsure to the category “no dementia.”
^†Dichotomizing the family physicians’ diagnoses by grouping the unsure to the category “dementia.”
^‡The registered symptoms were integrated by the researchers according to the DSM-III-R criteria.
LR+, positive likelihood ratio; LR–, negative likelihood ratio; NPV, negative predictive value; PPV, positive predictive value; SE, sensitivity; SP, specificity.

TABLE 3

Univariate associations of each documented variable by the family physicians

	Dementia
	Absent	Present	OR (95%CI)	P
Clinical findings by family physician
Cognitive symptoms
(0–12), mean (SD)	7.6 (5.2)	9.8 (4.6)	1.13 (1.03–1.24)	.01*
ADL dependency, %	25	75	3.53 (1.46–8.56)	.01*
Somatic comorbidity, % †	88	67	0.27(0.08–0.89)	.03*
Blood abnormality, % ‡	21	42	2.84 (1.07–7.55)	.04*
Behavioral changes, %	41	68	0.74 (0.54–1.02)	.07*
Duration of symptoms, years (SD)	1.5 (0.8)	1.9 (1.0)	1.77 (1.07–2.94)	.03*
Family physicians’ performance
Number of consultations, mean (SD)	3.9 (3.4)	3.5 (3.6)	0.97 (0.86–1.09)	.60
Home visit, %	35	43	1.39 (0.58–3.33)	.46
Recommendations applied, mean (SD)	24.5 (3.4)	25.0 (3.7)	1.04 (0.92–1.17)	.57
MMSE used, %	21	15	0.69 (0.23–2.07)	.51
Informant contacted, %	65	83	2.67 (1.01–7.11)	.05*
Familiar with patient, %	79	84	1.41 (0.47–4.21)	.54
Family physician–patient relation, >5 years, %	65	75	0.60 (0.24–1.50)	.27
Patient characteristics
Mean age, years (SD)	73 (8.7)	74.3 (6.3)	1.03 (0.97–1.09)	.41
Male sex, %	44	44	1.00 (0.42–2.34)	.99
n = 93. Values are in means (SD) or percentages.
*P
^† Sensory impairment, internal dysfunction; neurologic dysfunction; intoxication; adverse drug effect, sum score of dichotomous items.
^‡ Hematology (hemoglobin; hematocrit; mean cell count; erythrocyte sedimentation rate); biochemistry (glucose; creatine; thyroid function), sumscore of dichotomous items.
ADL, activities of daily living, 1 question scored on a 4-point scale; CI, confidence interval; MMSE, Mini-Mental State Examination; OR, odds ratio.