Getting acquainted with labs 101

Many times students are overwhelmed looking at a cumulative lab report, wondering what does it all mean and what is important. Often lab tests are integrated with various disease processes throughout the curriculum and therefore you look at one or two values at a time not looking at the big picture and how values are related. From the very beginning of your clinical experience you should evaluate lab values as part of your assessment of the patient. To do a general overview look at the groups of labs for abnormalities, if there are none that's good and move on, but if there are abnormalities in that group you will have an idea of what to be concerned about. Discuss with your instructor, primary nurse, and the physician. Medicine is very specialized these days; sometimes the Cardiologist overlooks the UA results.

Look at important groups of chemistries:

Electrolytes—Think electrical activity! Electrical activity in the human body includes important items such as nerve impulse transmission and depolarization / repolarization of muscles (including the heart). Disturbances can effect mental status, induce seizures, induce cardiac dysrhythmias, change the effect of antidyrsrhythmic drugs, cause muscle excitation or weakness. (Look at Potassium, Sodium, Chloride, Calcium, Magnesium)

Indicators of Renal Function—Kidney function is vital and somewhat tenuous in the elderly population. The kidneys remove waste products from the body and in some cases excrete drugs. Delayed drug excretion could lead to toxicity. Monitor renal function (Look at Creatinine and BUN) carefully, especially if your patient is undergoing any procedures using contrast dye. Any x-ray exam ending in "ography" tend to use contrast medium that is hard on the kidneys, such as angiography. Protein in the urine also indicates kidney problems.

Indicators of Diabetes—Diabetes is a risk factor for cardiovascular, kidney (look at indicators of renal function), and other disease processes. Identifying the presence of http://ads.associatedcontent.com/www...&cb=7b6f58b188diabetes (Look at Glucose), or the effectiveness of treatment (Look at Hgb A1C) is vital. Hemaglobin A1C gives an indication of average blood sugars for the past 3 months. If a diabetic patient is under good control blood sugars should be in the normal range. Spikes in blood sugars are seen with infections (Check WBC), changes in patient behaviors (might indicate neurological changes such as a patient admitted with high blood sugar because they are eating inappropriately due to advancing dementia)

Indicators of Liver Function—Another important organ for the removal of wastes and drugs. Liver enzymes (Look at ALT, AST, GGT, LDH) are usually inside the cell, they are elevated when there is cell damage/death and the enzymes escape increasing levels in the blood stream. Waste products (Look at Ammonia, Bilirubin) accumulate if the liver is not functioning well. Many plasma proteins are manufactured by the liver (Look at Albumin) as well at clotting factors (Look at PT / INR) which can lead to problems with fluid dynamics and coagulation. The liver is the major organ for drug biotransformation. This is the change drugs go through which either degrades or activates the drug. If the liver function is poor either the drug will accumulate or in the case of pro-drugs won't be transformed into a substance usable by the body (Look at drug levels).

Lab tests for Cardiovascular Disease—Cardiac enzymes should be mainly inside the cell and increase in the blood stream when cell damage / death occurs (Look at CK, Troponin). Elevated cholesterol levels are a risk factor for CV disease (Look at Total Cholesterol, HDL, LDL, Triglycerides). Another lab that may indicate risk for CV disease and helps in the diagnosis of congestive heart failure is BNP (B-type natriuretic peptide)

Coagulation Studies—these look at the ability to clot (PTT, PT / INR). Elevations indicate the patient has a greater chance of bleeding. Also look at platelets. If bleeding is occurring they will get used up or if a patient has decreased platelets for other reasons in combination with elevations of coagulation studies there is a greater risk of bleeding. Deep vein thrombosis and pulmonary embolus are examples of problems caused by the presence of undesirable clots (Look at D-Dimer).

Labs Indicating Inflammation—more and more inflammation has been found to play a role in major disease processes. ESR (Erythrocyte Sedimentation Rate) is a general indicator of infection that corresponds with the amount of inflammation. CRP (C-reactive protein) is an abnormal protein produced during acute inflammatory processes. It increases earlier than ESR and increases are seen when there is necrotic tissue (example myocardial infarct) in the body or infection.

Look at the CBC (complete blood count)

Labs related to Oxygenation—RBC's are responsible for oxygenation. Decreased RBC's equals decreased oxygen carrying capacity. This can result in fatigue, shortness of breath, and decreased healing. Because of their color, decreased cells can result in pallor. Red cells are by far the cell type of the greatest number in the blood. Increased levels increase blood viscosity, micro-infarcts and hypertension. (Look at RBC, HGB, HCT) Characteristics (size, weight, color, range of cell sizes) of the red cells are measured by indices (Look for MCV, MCH, MCHC, RDW). Increased numbers of immature red cells (Look for Reticulocyte Count) indicates increased red cell production which depending on the etiology could be a good (example: positive response to anemia treatment) or bad thing (polycythemia vera).

Labs related to Immune Function—WBC's are the backbone of the immune system. Increases indicate the presence of infection while decreases indicate the inability to fight infection. Alterations high or low can also occur with leukemias. In this malignant disease process what ever the amount of white cells present there is still an increased risk of infection. The Differential is a breakdown by percentage of the white cell types. Elevation in particular types can infer a type of infection (examples: elevated Neutrophils, bacterial infection, increased Lymphocytes, viral infection)

Labs related to clotting—Platelets are the cell component of clots. Decreased levels may result in bleeding (check RBC, HGB, HCT) or be a result of bleeding (Platelets get used up trying to stop bleeding by forming clots). Increased levels may result in unwanted clots. Platelets are attracted by and become more likely to aggregate by the presence of inflammation (Check for labs indicating inflammation).

Urinalysis: The urinary tract is a common site for infections and a major cause of sepsis in the elderly and disabled.