Cholesterol, thyroid, and professional standards

Cholesterol testing

Cholesterol is a fatlike substance (lipid) present in cell membranes. It is needed to form bile acids, steroid hormones, the coverings of our nerves, and some of our brain tissue. Cholesterol travels in the blood as distinct particles containing both lipids and proteins. These particles are called lipoproteins. The cholesterol level in the blood is determined partly by inheritance and partly by acquired factors, such as diet, calorie and nutrient balance, and level of physical activity.

Patients often are confused by cholesterol testing. Cholesterol is often a catchall term for both the cholesterol a person eats and the cholesterol that is produced in the body. A high blood level of low-density lipoprotein (LDL) cholesterol reflects an increased risk of heart disease. LDL cholesterol is often referred to as “bad” or “lousy” cholesterol. Lower levels of LDL cholesterol reflect a lower risk of heart disease. When too much LDL cholesterol circulates in the blood, it can slowly build up in the walls of arteries that feed the heart and brain. Together with other substances, it can form plaque, a thick and sticky deposit that can clog arteries. This condition is known as atherosclerosis. If a blood clot (thrombus) forms at the site of plaque, blood flow can be blocked in the coronary arteries of the heart muscle, causing a heart attack. If a clot blocks blood flow to part of the brain, a stroke may result. LDL results are often interpreted as follows:

LDL >100 mg/dL = Optimal

LDL 100–129 = Near or above optimal

LDL 130–159 = Borderline high

LDL 160–189 = High

LDL 190+ = Very high

About one-third to one-fourth of blood cholesterol is carried by high-density lipoprotein (HDL). HDL cholesterol is known as “good” or “healthy” cholesterol. High levels of HDL cholesterol seem to protect against heart attack. HDL can carry cholesterol away from the arteries and back to the liver. It is believed that cholesterol is removed from the lining of the arteries when high levels of HDL exist. Low levels of HDL cholesterol (i.e., lower than 40 mg/dL) may result in a greater risk of heart disease.

Adults older than 20 years of age should have a cholesterol test at least once every 5 years. Total cholesterol and the combination of LDL and HDL typically are screened and monitored. All three tests are considered screening tests, and elevated results require additional testing. In general, total cholesterol levels under 200 mg/dL are considered normal. Results over 240 mg/dL are considered elevated and may place a person in the high-risk category for coronary heart disease. An HDL cholesterol level of 40 mg/dL or higher is considered acceptable for men, and values of 50 or higher are acceptable for women. HDL levels below 40 mg/dL for men and below 50 mg/dL for women place a person at risk of coronary heart disease.

Although total cholesterol and HDL cholesterol levels are not significantly affected by food consumption, most providers prefer that patients fast from food and liquids, with the exception of water, for 12 hours before cholesterol levels are checked. If the total cholesterol is elevated, the provider is likely to order a lipid profile, which is a series of tests that measures the total cholesterol, HDL and LDL cholesterol levels, and triglyceride levels. Triglycerides are fat in the blood related to caloric intake. Therefore, the patient must be instructed to fast from all food and alcoholic beverages 12 hours before the triglyceride test or lipid profiles. Consistently high triglyceride levels may lead to heart disease, especially in people with low levels of “good” HDL cholesterol and high levels of “bad” LDL cholesterol and in people with diabetes type 2. Elevated levels of triglycerides are typically stored in belly fat and are associated with central obesity.

CLIA-waived cholesterol monitors can measure total cholesterol from a fingerstick specimen. The Cholestech LDX analyzer performs a lipid panel and provides a risk assessment using a capillary blood sample (Procedure 34.7). This system uses a cassette testing device capable of measuring glucose, total cholesterol (TC), HDL, LDL, very-low-density lipoprotein (VLDL), triglycerides, and the TC/HDL ratio. It uses a combination of testing methods to detect the color changes caused by each of the lipid panel analytes.

Thyroid hormone testing

The thyroid gland is located anterior to the trachea in the throat. It produces the hormones triiodothyronine (T3) and thyroxine (T4). These hormones are essential for life and regulate body metabolism, growth, and development. The thyroid gland is influenced by hormones produced by two other glands found in the brain, the pituitary gland and the hypothalamus. The pituitary gland produces thyroid-stimulating hormone (TSH), and the hypothalamus produces thyrotropin-releasing hormone (TRH).

CLIA-waived rapid diagnostic tests are available to qualitatively measure TSH. These tests are available for point-of-care testing (POCT). Using whole blood from a fingerstick, CLIA-waived tests can screen patients for hypothyroidism, which is deficient activity of the thyroid gland. Hypothyroidism is indicated with elevated TSH levels. The tests use lateral flow immunoassay technology housed in a plastic cassette. One such commercially available test is the ThyroTest Whole Blood TSH Test.

Patient coaching

As with all other procedures, the laboratory test is only as valid as the specimen and the procedure performed on that specimen. You, as the provider’s agent, are responsible for that validity when you instruct the patient and when you perform the test. Be clear in your instructions. Give written materials to reinforce your instructions. Ask if the patient has any questions, and take the time and effort to answer the questions in a way that is clear and understandable to the patient. If the patient has additional questions that you cannot answer, have the provider talk to the patient directly.

Legal and ethical issues

A medical assistant who is responsible for POL testing must clearly understand the basic concepts of laboratory medicine. Therefore, you must stay current with the rapid technologic advances in laboratory medicine and help establish a protocol for testing that best suits your provider-employer.

You are responsible for properly collecting specimens and testing them accurately. Patient confidentiality is paramount when testing is performed, as is strictly conforming to all established quality control procedures.

Patient-centered care

The CMA plays an important role in the laboratory and patient care. Often many different tests are needed to assess a patient’s health. Many patients appreciate that they can have CLIA-waived tests done during a routine visit to their provider. With a simple fingerstick, a patient can have tests such as a hemoglobin and hematocrit, protime, A1c, blood glucose, cholesterol, and ALT/AST completed in the POL. Saving patients’ time and the inconvenience of going to a different location are just a few benefits of having a CLIA-waived POL. Also, having test results available quickly and while patients are still in the clinic gives them the opportunity to ask questions and have them answered on the spot.

Professional behaviors

An ever-increasing number of CLIA-waived hematology and chemistry blood tests are relatively simple to perform and require minimal training. This allows the provider to share the results with the patient quickly, which may lead to greater patient compliance with the prescribed treatment plan. Proper patient care demands attention to detail in all three areas of the testing process:

• Preanalytic: Proper care of the testing supplies and equipment, and proper patient identification and specimen collection
• Analytic: Running the tests according to the specific manufacturer’s instructions; recording and analyzing the controls and the patient results
• Postanalytic: Proper disposal of biohazard supplies; routing of test results to the provider and patient

Medical assistants are involved in all three areas of testing. They are responsible for the organization and documentation of each performed test on the appropriate lab flow sheet and in the patient’s health record.