This is the protocol for a review and there is no abstract. The objectives are as follows: To determine the diagnostic accuracy of state, minimally invasive clinical and physical signs (or sets of signs) to be used as screening tests for detecting impending or current water-loss dehydration, or both, in older people by systematically reviewing studies that have measured a reference standard and at least one index test in people aged 65 years and over. 1. To assess the effect of different cut offs of index test results assessed using continuous data on sensitivity and specificity in diagnosis of impending or current water-loss dehydration. 2. To identify clinical and physical signs that may be used in screening for impending or current water-loss dehydration in older people. 3. To identify clinical and physical signs that are not useful in screening for impending or current water-loss dehydration in older people. 4. To directly compare promising index tests (sensitivity _ 0.60 and specificity _ 0.75) where two or more are measured in a single study (direct comparison). 5. To carry out an exploratory analysis to assess the value of combining the best three index tests where the three tests each have some predictive ability of their own, and individual studies include participants who had all three tests. We will explore sources of heterogeneity of diagnostic accuracy of individual clinical and physical signs that show some evidence of discrimination by the reference standard used, cut off value for tests providing continuous data, type of participants (community dwelling older people, those in residential care, and those in hospital), sex, and baseline prevalence of dehydration.