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.