LII:The Comprehensive Guide to Physician Office Laboratory Setup and Operation/Primary laboratory testing domains in the POL

A wide variety of testing may be done in the physician office laboratory (POL), though much of it may be CLIA-waived testing. This chapter talks about the primary testing domains encountered in POLs. These testing domains seem to be relatively common in a POL and offer CLIA-waived tests.

This third chapter on the topic of primary testing domains has six sections.

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3. Primary Laboratory Testing Domains in the POL

Urinalysis

In June 2014, healthcare market research company Kalorama Information estimated that by volume, dipstick urinalysis easily was the most common test type in the POL. Urinalysis' popularity in the POL is in part due to advanced technology, low cost, and high market competition, which have in turn helped make many such in vitro diagnostic (IVD) tests eligible for CLIA's waived category. In fact, more than 1,200 CLIA waivers have been granted for dipstick urinalysis kits alone since 2004. Advances in CLIA-waived benchtop and portable dipstick readers have further improved dipstick interpretation accuracy and increased urinalysis test volumes in the POL.

Another perhaps more important reason for dipstick urinalysis' popularity in the POL is the sheer usefulness of the IVD tool. The College of American Pathologists (CAP) have referred to the urine dipstick as "a remarkable 'lab-on-a-strip'" for its ability to "help detect infection, bleeding, diabetes, and other problems." For example, the pH, specific gravity, and protein prevalence as well as the presence of constituents such as bilirubin, glucose, and nitrites all can aid a physician in ultimately making a solid diagnosis. Even pregnancy can be determined using urine dipsticks specifically designed to detect the hormone human chorionic gonadotropin (hCG).

Basic concepts and collection procedures

The human urinary system is responsible for several tasks, including filtering blood, excreting waste, regulating pH, regulating blood pressure, and creating the hormone erythropoietin, which stimulates red blood cell production in the body. The system is composed of kidneys, ureters, the bladder, and the urethra, all of which play an important role in forming and excreting urine from the body. In short, blood passes through the kidney, and through capillary action much of the liquid of the blood is filtered out and collected, eventually passing through the ureters to the bladder and out the urethra.

When collected properly using quality assurance methods, the expelled urine then has clinical significance when analyzed using physical, chemical, and even microscopic procedures. Maintaining quality standards is vital, otherwise specimens could become contaminated or reach a state not ideal for testing. Clinical collection procedures encourage mid-stream collection of urine into a sterile, well-labeled container. The contents should be tested within an hour of collection or otherwise rapidly refrigerated. The implementation of standardized terminology, equipment calibration techniques, quality control procedures, and proper reagent storage techniques also help ensure test results and interpretation are as accurate as possible. And of course proper hand, eye, and body protection should be correctly used when handling urine.

Urine composition

Urine is composed predominately of water (95 to 96 percent), with the rest being made up of dissolved organic and inorganic solid waste. When collected over a 24-hour period, the average healthy adult's urine contains approximately 40 to 50 grams of dissolved solid waste. The primary constituents of that waste are, in order of prevalence (assuming a 1,400 mL sample):

• urea, the molecule CO(NH₂)₂ which acts as a primary carrier of waste nitrogen from protein breakdown in the body: 25.0 grams
• chloride, the anion Cl^- which is a vital electrolyte in the blood: 6.3 grams
• sodium, the cation Na⁺ which is vital to osmotic equilibrium in the body: 3.0 grams
• potassium, the cation K⁺ which is vital to proper neuron function and osmotic equilibrium: 1.7 grams
• creatinine, an endogenous byproduct of muscle creatine metabolism: 1.5 grams
• sulfate, the anion SO₄²⁻ which is a byproduct of protein turnover and the metabolism of several sulfur-containing compounds in food and water: 1.4 grams
• dihydrogen phosphate, the anion H₂PO^4- (as a titratable acid) excreted as a byproduct of renal acid-base regulation: 1.2 grams
• ammonium, the cation NH⁴⁺ which is excreted as a byproduct of renal acid-base regulation: 0.8 grams
• amino acids, organic compounds composed of amine (-NH2) and carboxylic acid (-COOH) that are building blocks of proteins: 0.8 grams
• uric acid, the compound C₅H₄N₄O₃ which is a byproduct of the breaking down of substances called purines in the body: 0.7 grams
• calcium, the cation Ca²⁺ which is vital to many functions of human biology: 0.2 grams
• magnesium, the cation Mg²⁺ which is vital to the nucleic acid chemistry of most life: 0.15 grams

Clinical laboratories set reference ranges for these constituents, and when a sample shows one or more of them outside of that reference range, the abnormality is often a sign of an ailment or problem in the body or with a diet. For example, the U.S. National Library of Medicine indicates the normal reference range for urea is 12 to 20 grams (though they also note "normal value ranges may vary slightly among different laboratories"), and numbers outside that range could indicate anything from kidney problems and malnutrition to too much protein in the diet.

Other constituents that normally aren't found in urine can make their way there, and their measurable presence are strong indicators of an underlying illness. Those constituents include:

• bilirubin, a bile pigment resulting from red blood cell breakdown that potentially indicates bile duct blockage, hepatitis, or cirrhosis
• erythrocytes, otherwise known as red blood cells, are a primary oxygen delivery vehicle, and their presence in urine potentially indicates a urinary tract infection or hemorrhage, prostate issues, or cancer of the bladder or kidney
• glucose, a sugar that is typically reabsorbed into blood in the kidney during filtering; its presence could indicate a type of diabetes or alimentary glycosuria
• hemoglobin, a protein found in red blood cells that when found in urine potentially indicate anything from kidney infection to tuberculosis
• ketones, byproducts of fat metabolism that potentially indicate diabetes mellitus or a dietary issue
• leukocytes, otherwise known as white blood cells, protect the body from infectious disease, and their presence in urine potentially indicates bladder or kidney infection
• protein, a building block of life, that when found in large quantities in urine could indicate heart and blood pressure problems, urinary tract problems, or dehydration
• urobilinogen, created from the breakdown of bilirubin, is also potentially indicative of bile duct blockage, hepatitis, or cirrhosis

• cells and crystals

Testing

• instruments and test kits

• CLIA-waived tests

Hematology/Blood collection

• hematology concepts

• introduction to blood collection and safety

• theory and collection procedures, including patient prep

• instruments and test kits

• CLIA-waived tests

Chemistry

• chemistry concepts

• instruments and test kits

• CLIA-waived tests

Immunology

• concepts in immunology

• instruments and test kits

• CLIA-waived tests

Microbiology

• common pathogens

• topics in microbiology

• instruments and test kits

• CLIA-waived tests

Toxicology

• topics in toxicology

• instruments and test kits

• CLIA-waived tests