Several tests are carried out daily on body fluids or tissue taken from patients in hospitals and clinics in order to establish the patient's health or disease state. Blood, semen, saliva, spinal fluid, lymph, perspiration, and urine are body fluids that may be tested to determine a subject's condition. Skin cells, cheek cells, biopsy tissue, and fecal samples are also routinely examined to make medical diagnosis. In addition, several diagnostic procedures are conducted on body fluids and tissues taken for the purpose of forensic analysis.
In the blood sampling field, many diagnostic systems are employed. One of the more commonly used systems involves the collection of blood from a vein through a needle assembly into an evacuated container. The evacuated container provides a pressure differential to facilitate the flow and collection of blood through the needle assembly into the container (Barnwell et al., U.S. Pat. No. 3,648,684). Most procedures of blood sampling and diagnostic testing require that blood be drawn into a vacuum tube that is then removed; subsequently portions of the sample are taken from the tube for diagnostic analysis.
Vessels that contain pre-determined amounts of reagents for use in diagnostic testing are well known. The use of such implements, however, requires one to pipette a sample by way of a measuring device not associated with the vessel. In sensitive assays prone to contamination, such as antibody diagnostic assays or the polymerase chain reaction (PCR), the use of pipettors or other devices that have been used in other laboratory procedures frequently leads to contamination of the assay and false positive results (PCR Technology, Principles And Applications For DNA Amplification, Erlich editor, W. H. Freeman Company Publishers, Page 4, 1992). One-step devices that draw blood by venipuncture and allow the blood to mix with chemicals in an attached reservoir have alleviated some of the contamination problems, but these devices draw a significant volume of blood and are not applicable to sensitive diagnostic tests that require a small amount of sample (Ayres, U.S. Pat. No. 3,874,367). Therefore, a disposable single assembly, diagnostic testing device that can be used for sensitive diagnostic testing without having to introduce a pipette or other measuring device is greatly needed.