Peritoneal fluid

• When you have abdominal pain and swelling, nausea, and/or fever and your healthcare practitioner suspects you have peritonitis or ascites.
• A sample of peritoneal fluid is collected by a healthcare practitioner with a syringe and needle using a procedure called paracentesis. 
• To help diagnose the cause of peritonitis, an inflammation of the membrane lining the abdomen, and/or peritoneal fluid accumulation, where fluid builds up in the abdomen or around internal organs (called ascites)

Pericardial fluid

• Pericardial fluid analysis: to evaluate and classify the type of fluid between the pericardium membranes to assist with diagnosis of infection or fluid balance disorder.
• Specimen: Pericardial fluid collected in a red- or green-top (heparin) tube for glucose, a lavender-top (EDTA) tube for cell count, and sterile containers for microbiology specimens; fluid in a clear container for cytology. Ensure that there is an equal amount of fixative and fluid in the container for cytology.
• Method: Spectrophotometry for glucose; automated or manual cell count, macroscopic examination of cultured organisms, and microscopic examination of specimen for microbiology and cytology; microscopic examination of cultured microorganisms.

Pleural fluid

• In a pleural fluid analysis, the doctor will remove fluid from the pleural membrane area by inserting a needle into the chest cavity and suctioning the fluid into a syringe (thoracentesis). This also works as a common procedure to drain the excess fluid from the chest cavity. The fluid will then be tested to determine the cause.
• Pleural biopsy involves taking a sample of tissue from the pleura. This can be done by inserting a small needle from outside the chest wall into the chest cavity.

Synovial fluid

• helps diagnosing the cause of joint inflammation, pain and/or swelling

• tested when one or more of the joints are swollen, red and/or painful

• a synovial fluid sample is obtained by inserting a needle into the space between the bones at a joint

• synovial fluid collection and analysis may be performed after fasting or at random

Saliva testing

• Saliva testing is a diagnostic technique that involves laboratory analysis of saliva to identify markers of endocrine, immunologic, inflammatory, infectious, and other types of conditions. 

• Saliva is a useful biological fluid for assaying steroid hormones such as cortisol, genetic material like RNA, proteins such as enzymes and antibodies, and a variety of other substances, including natural metabolites, including saliva nitrite. 

• Saliva testing is used to screen for or diagnose numerous conditions and disease states, as well as for drug testing. 

• Salivary testing has even been used by the U.S. government to assess circadian rhythm shifts in astronauts before flight and to evaluate hormonal profiles of soldiers undergoing military survival training.

Amniotic fluid

• To detect and diagnose certain birth defects, genetic diseases, and chromosomal abnormalities in a fetus, especially if prenatal screening tests are abnormal.

• A sample (about 1 ounce) of amniotic fluid is obtained using a procedure called amniocentesis that involves inserting a thin needle through the belly and uterus into the amniotic sac.

Cerebrospinal fluid

• CSF is formed by a combined process of plasma ultrafiltration and active secretion. 
• Mechanical and osmotic barriers exist between plasma and CSF and between CSF and brain. 
• Lumbar puncture is the preferred technique for CSF sampling. 
• Normal CSF should be clear, colorless, and free of clotted material. 
• CSF can be examined for presence of microbes using stains. 
• Additionally, the chemical composition of CSF can be examined; tests of interest include glucose, protein, lactate, enzymes, glutamine, specific amino acids, biogenic amines, and various drugs.

Urine samples

Type of urine sample             How it is used
First morning sample               Provides a concentrated sample of urine that contains the overnight
                                                 accumulation of metabolites. Useful for detection of proteins or
                                                 unusual analytes.
Random                                   Convenient sample that can be collected at any time.
                                                 Most often used for routine screening tests.
Timed                                       Typically 2 to 6 hours of urine output is collected to give a
                                                 representative sample; duration of collection depends on the
                                                 analytes.
24-hour                                    Entire urine output for a 24-hour period is collected. Like a timed
                                                 urine, but used for metabolites whose excretion rates may vary with
                                                 time of day and full 24-hour collection is needed to be representative.

Blood collection tubes

TUBE ADDITIVE            STOPPER COLOR           SAMPLE             COMMENT
None                                Red                                   Serum                Clotting requires at least 30                                                                                                                     minutes at room temperature Silica clot activator         Red/black                          Serum                  Silica speeds the clotting 
                                                                                                             process compared to no
                                                                                                             activator
Thrombin                        Gray/yellow                      Serum                  Speeds clotting process
                                                                                                             significantly to produce serum in
                                                                                                             several minutes — used mostly
                                                                                                             for urgent (STAT) testing Lithium Heparin              Green                                Plasma                 Preferred plasma sample for
                                                                                                             most chemistry tests — not
                                                                                                             suitable when testing for lithium Sodium Heparin              Green                                Plasma               Used when testing for lithium—
                                                                                                             not suitable when testing for
                                                                                                             sodium
EDTA                               Lavender                          Plasma               Occasionally used for some
                                                                                                             chemistry tests and typically
                                                                                                             used for Hematology
Potassium EDTA
in special plastic tube      Tan or brown                    Plasma                For blood lead testing;
                                                                                                             tubes are certified to have very                                                                                                               low levels of contamination by                                                                                                                 lead
Sodium fluoride/
potassium oxalate            Gray                                  Plasma               For glucose testing — sodium
                                                                                                             fluoride inhibits metabolism of
                                                                                                             glucose by white blood cells