The healthcare provider conducts or assists with certain diagnostic procedures. Examples of the types of assisted procedures include endoscopy, lumbar puncture, and cardiac catheterization. Diagnostic procedures often performed independently of other healthcare providers include Papanicolaou (Pap) test, centrifugation of blood samples, ECG, breathing tests, and pulse oximetry.
Collecting specimens and conducting procedures are the main interventions in the diagnostic pretest and intratest phases. Procure, process, transport, and store specimens properly. The community environment and healthcare settings in which testing takes place dictate protocols for doing this. Everyone involved in the process must have a thorough understanding of testing principles and protocols and must adhere to them to ensure accurate results.
Determine specimen type needed and method of sample procurement. Obtain any special equipment and supplies that are necessary (e.g., sterile containers, special kits).
There are three methods of collection: collection by the patient, supervised collection, and collection by the healthcare provider. Collection by the patient requires patient cooperation, understanding, and instruction. It does not always require direct supervision, as in a routine urine sample collected by the patient privately. Supervised collection requires supervision of the patient by trained personnel during specimen collection, as in a urine sample procured in a supervised setting for drug screening. An example of the third method of collection, in which the healthcare provider performs the entire collection, is aspirating a urine sample from an indwelling catheter.
Time of collection is also important. For example, results from a fasting blood glucose test versus results from a glucose tolerance test are significantly different as diagnostic parameters.
Specimens can be rejected for analysis because of factors related to the specimen itself or to the collection process (Table 1.6).
Blood collection is normally done by trained persons. (An exception is the self-test for capillary blood glucose using equipment designed specifically for that purpose.) The time of collection is an important factor (e.g., a sequence of samples for a cardiac panel). For example, a peak drug level blood specimen is collected when highest drug concentration in the blood is expected. This type of test is used for therapeutic drug management and dosing. Conversely, a trough sample is collected when lowest drug concentration is expected. These types of tests are used for therapeutic drug monitoring, and specimens are collected and results reported before the next scheduled dose of medication.
Legal and forensic specimens are collected as evidence in legal proceedings, for criminal investigations, and after death. Examples include DNA samples and drug and alcohol levels. Factors such as chain-of-custody situations and witnessed collections may be involved.
The following list addresses some general comments about specimen collections:
Stool and urine collection requires clean, dry containers and kits.
Timed urine collection requires refrigeration or containers with special additives (preservatives).
Sterile, dry containers and special kits are needed for midstream clean-catch urine specimens.
Oral, saliva, and sputum specimens require specific techniques and kits and, sometimes, special preservatives.
Blood collection equipment includes gloves, needles, collection tubes, syringes, tourniquets, needle disposal containers, lancets for skin puncture, cleansing agents or antimicrobial skin preparations, gauze, and adhesive bandages.
Color-coded stoppers and tubes indicate the type of additive present in the collection tube (Table 1.7).
Additives preserve the specimen, prevent deterioration and coagulation, or block action of certain enzymes in blood cells.
Tubes with anticoagulants should be gently and completely inverted (end over end) 7–10 times after collection. This process ensures complete mixing of anticoagulants with the blood sample and prevents clot formation.
Store specimens properly after collecting or transport them to the laboratory immediately for processing and analysis if possible. Failure to do so may result in specimen deterioration. STAT-ordered tests should always be hand delivered to the laboratory and then processed as STAT.
Unacceptable specimens lead to increased costs and time wasted in getting results to the healthcare provider, patient, institution, and third-party payer. Exposure to sunlight, air, or other substances and warming or cooling can alter specimen integrity. Check with the laboratory for proper storage (e.g., ice, ice water, separate from ice), transport, and time limits.
As environments for specimen collection become more variable, modified procedures and protocols require the healthcare provider to keep abreast of the latest information related to these factors.