## 4 Discussion
The MMSE paper-and-pencil test showed a pooled sensitivity of 85% and a specificity of 86% in a non-clinical community setting [79]. The SLUMS paper-and-pencil test for detecting MCI in patients with less than a high school education had a sensitivity of 92% and a specificity of 81%, and in patients with a high school education or more, a sensitivity of 95% and a specificity of 76% [17]. Despite the relatively high sensitivity and specificity levels, these instruments are not the gold standard for cognitive assessment and, therefore, their use might have affected the sensitivity and specificity calculations of the index test and, certainly, undermines the confidence in the reported results. The early detection of cognitive impairment is critical to an early intervention [12; 13]. Index tests with high sensitivity levels are essential when the goal is to identify a serious disease with available treatment [44; 80]. Digital solutions emerge as a valid alternative for cognitive screening, potentially enhancing cognitive screening and monitoring in the general and clinical population, since most do not require the presence of a trained professional and have an automatic digital screening system and scoring [52; 62; 76], decreasing the costs associated with their use and facilitating the screening for high numbers of individuals. Digital solutions can be valuable in neuropsychological assessment, enabling the development of large-scale, norm-based, and technology-driven tests [28]. These tools produce large cognitive datasets that can be informative through machine learning and big data analysis, contributing to the detection of patterns and declines in cognitive performance [28]. The accuracy estimates of sensitivity, specificity, and the false positive rate found in this meta-analysis suggest that digital solutions have satisfactory accuracy and the potential to be used as instruments for cognitive screening. However, these estimates must be interpreted and compared with caution, since the GRADE evidence assessment and rating of these accuracy estimates mainly showed a low quality of evidence. The risk of bias and inconsistency found in the GRADE assessment downgraded the quality of the evidence. The quality of the included studies as evaluated by the QUADAS-2 tool suggests a risk of bias in the patients' selection domain, including for those studies presenting the digital index tests with higher sensitivity/specificity values. A test accuracy study with a high risk of bias in the participant selection domain can give inflated estimates of sensitivity and specificity [81]. Despite the different definitions used by the studies, we found relative homogeneity in the target condition, as they all focus on the diagnostic ability and accuracy when screening for cognitive impairment. Nevertheless, the reference standards display substantial methodological heterogeneity. This heterogeneity was due to significant variations in the instruments adopted and/or the clinical assessment process followed across the studies. A similar reference standard, preferentially a gold standard, should be applied across studies to facilitate accuracy comparisons and increase the confidence in the results [39]. Considering the heterogeneity in reference standards and index tests across studies, the meta-analysis estimates have limitations, and the interpretation and comparison of estimates should be performed cautiously [43]. Also, the high risk of bias in the patients' selection downgraded the quality of the evidence. When applying the GRADE approach, overall, there was a serious risk of bias due to less robust procedures regarding patient selection, the index test, and reference standard domains, and consequently, the quality of evidence was downgraded by one level in this domain. The high heterogeneity of the outcomes of the included studies also prompted the downgrading of the evidence due to inconsistency by one level. These aspects must be considered in the design of cognitive diagnostic accuracy studies to improve the quality of the evidence.