The Terminology- SNOMED CTÂ®, an Evolving Clinical Reference Terminology. SNOMEDÂ® is the Systemized Nomenclature of Medicine. It is a controlled medical terminology (CMT). At its simplest, a SNOMED is a coded vocabulary of medical concepts and expressions used in healthcare.
The partial thromboplastin time (PTT) is a screening test that helps evaluate a person's ability to appropriately form blood clots. It measures the number of seconds it takes for a clot to form in a person's sample of blood after substances (reagents) are added.
When an initial PTT is prolonged, a second PTT test is performed by mixing the person's plasma with pooled normal plasma (a collection of plasma from a number of normal donors). If the PTT time returns to normal (corrects), it suggests a deficiency of one or more of the coagulation factors in the person's plasma. If the time remains prolonged, then the problem may be due to the presence of an abnormal specific factor inhibitor (autoantibody) or nonspecific lupus anticoagulant.