EPV is valuable in the evaluation of tests like bacterial cultures in patients having a respiratory tract infection. However, EPV might be valuable in other situations evaluating other tests.

There are many clinical situations where EPV might add diagnostic information. Below are listed some examples evaluating microbiological diagnostic tests (Table I) as well as other examples evaluating other tests than microbiologic diagnostic tests (Table II).

Table I. Example of clinical situations evaluating microbiologic diagnostic tests where the EPV might add diagnostic information.
Symptom	Disease	Test to be evaluated	Etiology	Sensitivity^a
A sore throat	A sore throat caused by GABHS	Throat culture	GABHS	GABHS in the throat
A sore throat	A sore throat caused by GABHS	A rapid test to detect presence of GABHS	GABHS	GABHS in the throat
A sore throat	A sore throat caused by H. influenzae	Nasopharyngeal culture	H. influenzae	H. influenzae in the nasopharynx
Long-standing cough	Long-standing cough caused by H. influenzae	Nasopharyngeal culture	H. influenzae	H. influenzae in the nasopharynx
Long-standing cough	Long-standing cough caused by M. catarrhalis	Nasopharyngeal culture	M. catarrhalis	M. catarrhalis in the nasopharynx
Frequent urge to urinate	Frequent urge to urinate caused by E. Coli	Urine culture	E. Coli	E. Coli in the urine
Increasing confusion among elderly institutionalized patients	Increasing confusion caused by E. Coli	Urine culture	E. Coli	E. Coli in the urine
^a	Sensitivity of the test to be evaluated established with a gold standard predicting presence of… To calculate EPV this sensitivity is used together with information about the proportion of positive tests among patients and healthy controls.

Ronny Gunnarsson MD PhD
Department of Primary Health Care
Göteborg University
SWEDEN

Table II. Example of clinical situations, not including microbiologic diagnostic tests, where the EPV might add diagnostic information.
Symptom	Disease	Test to be evaluated	Etiology	Sensitivity^a
Low back pain	Low back pain caused by a herniated disc in the lumbar region	Specific pattern on a non invasive diagnostic method, for example ultrasound	Herniated disc in the lumbar region	Herniated disc in the lumbar region
Low back pain	Low back pain caused by a herniated disc in the lumbar region	Pain reaction when performing a specific orthopaedic diagnostic manoeuvre	Herniated disc in the lumbar region	Herniated disc in the lumbar region
Chest pain	Chest pain caused by coronary heart disease	A specific EKG-pattern	Coronary heart disease	Coronary heart disease
Pelvic pain	Pelvic pain caused by lactose intolerance	Questionnaire specific for symptoms caused by lactose intolerance	Lactose intolerance	Lactose intolerance
^a	Sensitivity of the test to be evaluated established with a gold standard predicting presence of… To calculate EPV this sensitivity is used together with information about the proportion of positive tests among patients and healthy controls.