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“Don’t know” sign: description and evaluation of its diagnostic accuracy for cognitive impairment

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Abstract

Objectives

Patients in neurology clinics are sometimes not aware of the reason for the consultation, and we have called this circumstance the “Don’t know” sign (DKS). Our objective was to define this new sign and its modalities and to evaluate its prevalence and its diagnostic accuracy for cognitive impairment (CI) in comparison to other observation-based signs.

Design, setting, and participants:

A cross-sectional prospective study included all new outpatients evaluated by the authors at neurology consultation.

Measurements

We recorded observation-based signs. The Global Deterioration Scale (GDS) was used to assess the cognitive status of patients, based on clinical history, caregiver interview, and cognitive test results. We analyzed the prevalence and the diagnostic accuracy for CI of DKS, “head turning sign,” “attending with,” verbal repetition, and combinations, calculating sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV).

Results

We enrolled 673 consecutive patients (62% female) with a mean ± SD age of 59.3 ± 20.2 years. DKS was positive in 94 patients (14%) and was strongly associated with GDS score. DKS had a Se of 0.41, Sp of 0.98, PPV of 0.89, and NPV of 0.79 for CI diagnosis. The presence of at least two positive observation signs yielded a Se of 0.50, Sp of 0.97, PPV of 0.86, and NPV of 0.81.

Conclusions

DKS is frequently observed in neurology outpatients. It has low sensitivity but high specificity and PPV for CI diagnosis. It does not require additional consultation time, and its use can be recommended in combination with other observation-based signs.

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Authors and Affiliations

  1. Neurology Unit, Hospital Universitario Virgen de Las Nieves, Granada, Spain

    Iago Rego-García, José Antonio Medina Gámez, Carmen Valderrama-Martín, Virginia Guillén Martínez, Rosa Vílchez Carrillo & Cristóbal Carnero-Pardo

  2. FIDYAN Neurocenter, Granada, Spain

    Cristóbal Carnero-Pardo

Authors
  1. Iago Rego-García
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  2. José Antonio Medina Gámez
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  3. Carmen Valderrama-Martín
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  4. Virginia Guillén Martínez
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  5. Rosa Vílchez Carrillo
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  6. Cristóbal Carnero-Pardo
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Contributions

Cristóbal Carnero-Pardo: conceptualization (lead), methodology (equal), data collection (equal), formal analysis (supporting), review and editing (equal). Virginia Guillén Martínez: data collection (equal), review and editing (equal). José Antonio Medina Gámez: data collection (equal), review and editing (equal). Iago Rego-García: methodology (equal), data collection (equal), formal analysis (lead), writing — original draft (lead); review and editing (equal). Carmen Valderrama Martín: data collection (equal), review and editing (equal). Rosa Vílchez Carrillo: data collection (equal), review and editing (equal).

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Correspondence to Iago Rego-García.

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Rego-García, I., Medina Gámez, J.A., Valderrama-Martín, C. et al. “Don’t know” sign: description and evaluation of its diagnostic accuracy for cognitive impairment. Neurol Sci 43, 993–997 (2022). https://doi.org/10.1007/s10072-021-05439-0

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  • DOI: https://doi.org/10.1007/s10072-021-05439-0

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