Which one of the following test is used for the diagnosis of Giardia lamlia infection?

Enterotest In this test patient is asked to swallow a gelatin capsule which contains a nylon thread at one end.The free end of the nylon thread is attached to the cheek of the patient.The capsule passes through the stomach to the duodenum.In the stomach ,the capsule is dissolved and thread remains in the duodenum and jejunum.After 2 hours the thread is withdrawn and placed in a tube containing saline and mechanically shaken.The centrifuged deposits of the saline is examined microscopically for motile trophizoites of G.lamblia.(refer pgno:32 baveja 3 rd edition)