Serial sevens (or, more generally, the descending subtraction task; DST), where a patient counts down from one hundred by sevens, is a clinical test used to test cognition; for example, to help assess

mental status The mental status examination (MSE) is an important part of the clinical assessment process in neurological and psychiatric practice. It is a structured way of observing and describing a patient's psychological functioning at a given point in t ...

after possible

head injury A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of in ...

, in suspected cases of

dementia Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...

or to show sleep inertia. This well-known test, in active documented use since at least 1944, was adopted as part of the mini-mental state examination. The test is also used in determining when a patient is becoming unconscious under anaesthetic, for example prior to major dental surgery. On its own, the inability to perform 'serial sevens' is not diagnostic of any particular disorder or impairment, but is generally used as a quick and easy test of

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'' ...

and

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered ...

in any number of situations where clinicians suspect that these cognitive functions might be affected. Each subtraction is considered as a unit and calculations are made on the basis of the 14 possible correct subtractions, that is 93-86-79-72-65-58-51-44-37-30-23-16-9-2. Similar tests include serial threes where the counting downwards is done by threes, reciting the months of the year in reverse order, or spelling 'world' backwards. A study involving uninjured high school athletes concluded that the serial sevens test is not appropriate when testing for

concussion A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include loss of consciousness (LOC); memory loss; headaches; difficulty with thinking, concentratio ...

because it lacks specificity; the pass rate is too low to give any meaningful result. The ability to recite the months in reverse order was thought to be a more effective measure because the pass rate was higher for that test in uninjured athletes. The numbers of the serial sevens test are a recurring motif in Sarah Kane's play ''

4.48 Psychosis ''4.48 Psychosis'' is the final play by British playwright Sarah Kane. It was her last work, first staged at the Royal Court's Jerwood Theatre Upstairs on 23 June 2000, directed by James Macdonald, nearly one and a half years after Kane's deat ...

''.

References

Cognitive impairment and dementia screening and assessment tools Cognitive tests Neuropsychological tests {{psych-stub