Laboratory Case Study

LABORATORY TESTS:  THEIR FUNCTION AND IMPORTANCE

In the past decade there has been a dramatic increase in both the number of new diagnostic laboratory tests as well as in the complexity of the tests offered.  This explosive growth in the field of laboratory medicine has been due to the demand by physicians for new and improved diagnostic procedures, combined with the ever-expanding capacity of modern technology to meet the demand with increasingly sophisticated laboratory methods and equipment.

On a daily basis medical transcriptionists come in contact with dictation which details the results of laboratory tests performed on patients.  In order to accurately transcribe this material, it is important to be familiar with the names and abbreviations of many laboratory tests, the reasons they are offered, and the meaning of the results.

Laboratory tests can be performed in many different settings:  clinics, physicians’ offices, health fairs, and sometimes even at home by the patient himself, but the greatest number of laboratory tests are performed within the hospital setting.  Hospital laboratories are equipped with the most technologically advanced and automated equipment to handle hundreds of tests each day.  The largest hospitals perform all standard laboratory tests, as well as many uncommon ones, which may be requested by smaller hospitals or clinics whose facilities are not equipped to handle unusual tests.

The laboratory of a hospital is divided into many smaller departments which perform specialized laboratory tests.  This division of labor is also reflected to a great extent on the average laboratory slip which is used to report the results of laboratory tests.  Various sections on the lab slip include hematology, blood bank, chemistry, coagulation, urinalysis, stool examination, microbiology, and cytology.

Hematology is concerned with the study of the formed components or cells of the blood.  These cells include mature red blood cells, white blood cells, and platelets, as well as their immature forms.  The function of the red blood cell is to carry oxygen from the lungs to the body tissues.  The function of the white blood cell is to fight any foreign substances that enter the body, such as bacteria.  Platelets function along with the coagulation factors in the blood to form a blood clot at the site of tissue injury.  White blood cells are further differentiated into groups which have diagnostic value.  These include lymphocytes, monocytes, neutrophils, eosinophils, basophils, and bands or immature neutrophils.  In the jargon, lymphocytes are also called lymphs, monocytes are called monos, eosinophils are known as eos, and basophils as basos.  Neutrophils have several different names, all derived from the fact that their cell nuclei are lobulated into segments.  Neutrophils are known as segmented neutrophils or simply as segs.  The more formal name for the neutrophil is the polymorphonucleated leukocyte.  ‘Polymorphonucleated’ means ‘many-shaped nucleus’, and ‘leukocyte’ means ‘white blood cell’.  This long term is frequently abbreviated as ‘PMN’ or also as ‘poly’.  So the terms neutrophil, seg, PMN, or poly all refer to the same type of white blood cell.  In addition, the laboratory slip identifies many other abnormal blood cells which can be identified under the microscope.  These are usually indicative of disease conditions.  Unusual red blood cells include sickle cells, target cells, anisocytes, and poikilocytes.  Unusual white blood cells include myelocytes and myeloblasts, which are noted in leukemia.  A complete count, abbreviated CBC, includes tests which measures red blood cell and white blood cell levels.  A CBC with differential also measures the levels of all of the different types of white blood cells as mentioned above.  Other common tests are the hemoglobin and hematocrit, often dictated as H&H, which are indicative of the oxygen-carrying capacity of the blood as well as the percentage of red blood cells per blood sample.  Normally the hematocrit is about 3 times greater than the hemoglobin level for the same patient, so that if the patient’s hemoglobin level was reported as 15, you could expect that the hematocrit would be approximately 45.

The blood bank tests blood samples to determine a patient’s blood group and Rh type.  Classification of blood groups is determined by the presence or absence of markers known as antigens on the surface of a person’s red blood cells.  These are genetically determined so that a person’s blood group never changes.  The most important classification is the ABO blood group system, which was discovered in the 1920s.  An individual’s blood group is reported as type A, type B, type AB, or type O.  Another important classification is that of the Rh group which was discovered in 1940.  When an Rh antigen is present on the surface of the patient’s red blood cells, that person is said to be Rh positive.  A patient without this antigen is called Rh negative.  The blood bank identifies each patient’s blood type and, if the physician orders it, matches it to compatible blood stored in the blood bank in case blood is needed for transfusion.  This entire procedure is known as typing and crossmatching.

The chemistry section of the laboratory performs tests on many different electrolytes, fats, and other substances found in the serum, or clear fluid which separates from a clotted blood sample.  Blood chemistries include tests for the electrolytes:  Sodium, potassium, calcium, and chloride.  Fats include cholesterol, triglycerides, and low-density lipoproteins called LDL.  Other substances tested include bilirubin, SGOT, SGPT, and LDH, which are used to evaluate liver function.  Blood urea nitrogen, abbreviated BUN, and creatinine are useful indicators of kidney function.  Uric acid levels are tested to diagnose the medical condition of gout.  Often the physician orders a combination of tests under 1 name.  For example, by checking a box next to the entry “serum lipid profile” on the laboratory slip, the physician can order the tests for cholesterol, triglycerides, total lipids, and lipoproteins.  An elevated serum acid phosphatase is useful in detecting prostatic cancer.  Blood glucose is frequently measured, particularly in diabetic patients.  In the hospital this may be done with automated equipment, or it may be tested directly by the physician, nurse, or even by the patient by using a Dextrostix, a plastic stick with a chemically treated paper tip which changes color to correspond to various blood glucose levels.  Only a drop of blood from a fingerstick is necessary to perform this test.

Laboratory tests which measure coagulation determine how quickly a patient’s blood clots when compared to normal values.  The 2 common coagulation tests are the prothrombin time, abbreviated PT, and the partial thromboplastin time, abbreviated PTT.

Blood tests can also be done to verify pregnancy, detect the presence of mononucleosis, syphilis, or hepatitis, and to determine the status of the thyroid gland and hormones produced in other organs.

Urinalysis is performed to measure levels of glucose, ketones, protein, or blood, and to microscopically identify white blood cells, red blood cells, and casts in the urine.  Ketones are the by-products of incomplete fat metabolism which occurs in diabetes when insulin levels are insufficient to metabolize glucose.  When present in the urine, they indicate that a patient’s diabetes is not under control.  Protein in the urine, also known as proteinuria, indicates damage to the nephron as a result of chronic inflammation or scarring or acute injury.  Blood in the urine, also called hematuria, is a result of infection, trauma, or cancer.  White blood cells in the urine, particularly neutrophils, are indicative of an acute infection in the bladder or kidneys.  The concentration of the urine compared to distilled water is expressed as a numerical value referred to as specific gravity.  Overall kidney function can be assessed by collecting a 24-hour urine specimen and measuring levels of creatinine.  Urine can also contain mineralized material in the form of crystals.  Crystals are most often formed from calcium and can grow into kidney stones, also known as renal calculi, which may lodge in the kidney or the ureter, causing extreme pain and obstruction of urine flow.

Stool samples are examined for occult or hidden blood as well as for parasitic worms or their eggs, ameba, bacteria, and fat content.

The microbiology department of the laboratory identifies infectious organisms through the use of microscopes and culture and sensitivity testing.  Specimens for testing are obtained from urine, stool, blood, sputum, wound drainage, or other body fluids.  A sample of the specimen is smeared onto a culture medium and incubated at 37 degrees Centigrade for sufficient time to allow bacterial growth to occur.  Antibiotic discs placed on the media of the culture plates permit evaluation of the sensitivity of the bacteria cultured to specific antibiotics.  Antibiotic discs to which the bacteria are sensitive are surrounded by a ring or zone of inhibition of bacterial growth.  Bacteria that are resistant to an antibiotic will show no inhibition of growth around the disc.  A rapid method to tentatively identify a pathogenic bacterium is to smear a sample on a slide and then stain the slide with a Gram stain.  This stain differentiates between organisms that are gram-positive and gram-negative.  The shape of the bacterium can provide further clues to the identity of the organism.  The acid-fast stain is a specialized stain which is used to specifically identify Mycobacteria.

Cytology is the study of cells.  Cells obtained from sputum samples, smears of the cervix, samples of cerebrospinal fluid, and from tissue biopsies are examined under a microscope for evidence of various abnormalities, but most specifically for signs suggestive of cancer.  Cells may be obtained by aspirating a lesion or by washing or brushing or scraping the mucous membranes of a structure, such as the cervix or the bronchus.

Physicians order laboratory tests to be performed on patients for several different reasons which we will discuss below.

1. Laboratory tests are performed to diagnose disease in a patient who is ill.  Along with the history and physical examination, laboratory tests form the basis for a sound medical diagnosis.  In a patient with a sore throat, a throat culture would be ordered to determine whether or not the patient had a bacterial infection of the throat, and if such an infection were present, to determine which antibiotics would be effective in treatment.

2. Laboratory tests are performed on apparently healthy patients to screen for hidden diseases.  Well-known examples include use of the Papanicolaou smear to identify cervical cancer, and the self-administered test for occult or hidden blood in the stool as an indicator of colon cancer.

3. Laboratory tests are used to assess the extent of damage from disease processes.  When a patient is suspected of having a heart attack, also called myocardial infarction, the physician will order a special test which measures the levels of specific substances which are released from damaged heart cells.  These substances are collectively known as cardiac isoenzymes, which include lactic dehydrogenase and creatine phosphokinase, also called CPK.

4. Laboratory tests are used to monitor the effectiveness of treatment prescribed by the physician.  For the diabetic patient receiving injections of insulin, glucose levels are monitored to insure that a normal balance is maintained between insulin levels and blood sugar, or glucose in the blood.

5. Laboratory tests are used to monitor blood levels of certain medications.  With some drugs it is of vital importance to know that the level of the drug in the bloodstream is within a therapeutic range.  For example, a patient taking Dilantin may experience an epileptic seizure if the level of the drug falls below the therapeutic range.  On the other hand, a patient in congestive heart failure being treated with digoxin can easily develop blood levels of the drug that are above the therapeutic range and, as a result, develop severe symptoms of toxicity.  Periodic monitoring of blood samples can insure the drug levels in the blood remain within the therapeutic range.

6. Laboratory tests can be used to monitor the course of a disease.  The flare-ups and remissions of rheumatoid arthritis can be followed by monitoring the rise and fall of the erythrocyte sedimentation rate, abbreviated as ESR.  The erythrocyte sedimentation rate measures the time required for erythrocytes, or red blood cells, to settle to the bottom of a test tube of standard diameter.

Laboratory test results are measured and reported most often using the metric system.  Common units of measure include centimeters, millmeters, cubic centimeters, milliliters, grams, milligrams, micrograms, milliequivalents, and percentages.

Laboratory test values are reported as numerical values.  If the value falls within the range observed in normal individuals, it is considered normal.  If it falls outside of this range, it is considered abnormal.  The age and sex of a patient cause variation in the normal range of laboratory values.  The accepted normal range for a particular laboratory test varies from one laboratory to another due to differences in equipment and methodology used in testing.  Therefore, laboratory slips usually give the accepted normal range for that particular laboratory facility.  The normal value is printed next to the blank space for the reported value for the individual patient.  When transcribing, it is not unusual for the medical transcriptionist to hear the physician say, “Normal for our laboratory is ...,” after dictating a patient’s test results.

The transcription of laboratory test terminology presents certain challenges.  There are many facets with which the medical transcriptionist must become familiar.  Correctly transcribing the name of a laboratory test or its abbreviation is just the first step.  Numerical results must be transcribed with absolute accuracy.  Care must be taken to accurately place decimal points and to correctly transcribe units of measure.  It is also necessary to understand why a test was ordered and what the results indicate.  Some dictations contain considerable detail concerning the test process, the use of special stains or dyes, as well as the significance of the results.  As a student, you will want to diligently study this critical area of medical transcription.  As a practicing medical transcriptionist, you will always be increasing your knowledge of laboratory tests and procedures as the technology of medicine increases daily.

The following dictations are brief examples of dictated laboratory tests results as found in the medical record.

The following are 4 original dictations of excerpts from laboratory procedures.

Dictation #1:  LABORATORY DATA:  The laboratory data revealed the sugar to be 179, but IVs were going.  Cholesterol was 370 and triglycerides 589.  Her HDL was only 33, and her LDL was 174.  Her LDL/HDL ratio was 5.3.  Her thyroid parameters were normal.  Her hemoglobin was 12.6 and her white count 7200.

Dictation #2:  LABORATORY FINDINGS:  Chemistry panel revealed an elevated BUN of 24.7, her cholesterol was 240, her SGOT was 49.  Urine culture revealed no growth; however, urinalysis showed 6 to 10 white cells and 8 to 12 red cells per high-power field.  There was 2+ bacteriuria noted.  CBC showed a white count of 7500, a hemoglobin of 12.4 g, and a normal differential.

Dictation #3:  SIGNIFICANT LABORATORY DATA:  Electrolytes on admission were normal, with a slightly elevated sodium at 148.  BUN 125, creatinine 3.8, with the BUN and creatinine falling to 82 and 2.8, respectively.  CBC on admission showed a white count of 12,500, hemoglobin 16.9, and hematocrit 51.0 due to hemoconcentration, all of those falling with simple rehydration to a white count of 7.9, hemoglobin 12.9, and hematocrit 37.7.  Skin scrapings of a rash which developed showed typical mites and multiple ova of Acarus scabiei.

Dictation #4:  LABORATORY DATA:  Electrolytes:  Sodium is 133, potassium 4.8, chloride 100.  CO2 is 31.  Prothrombin time was 11.9.  PTT was 27 seconds.  Urine was clear.  CBC showed a white count of 8.3 thousand with no shift.  Hemoglobin and hematocrit were 14 and 40, respectively.

James L. Bennington, MD

Editor, Saunders Dictionary & Encyclopedia of Laboratory Medicine and Technology

(W. B. Saunders Co., Philadelphia)

Chairman, Department of Pathology and Clinical Laboratories

Children’s Hospital, San Francisco, CA.

FOOTNOTE

Line 6 (Page 2).  Cell nucleus is was changed to cell nuclei are for proper plural agreement.

Lines 10-12 (Page 2).  Words under discussion are enclosed in single quotation marks.

Line 24 (Page 2).  Although a physician may dictate the slang term H&H, the transcriptionist should translate it when it appears in a medical report.

Line 21 (Page 3).  Alternative:  Finger stick.

Line 6 (Page 4).  Alternative:  Amoeba.

Lines 15-21 (Page 4).  Alternative:  Disk, disks.

Line 23 (Page 4).  Gram’s stain was changed to Gram stain to correct the dictation error.  The terms gram-negative and
gram-positive are permanently hyphenated compound adjectives.  Although it is traditional to eliminate the hyphen in a compound adjective when it occurs after the noun, entries that appear as permanently hyphenated compound adjectives should retain their hyphens, no matter where they appear in a sentence.

Line 13 (Page 5).  Creatinine was changed to creatine to correct the dictation error.

Line 50 (Page 5).  Causes was changed to cause for plural agreement (age and sex ... cause).

Line 34 (Page 6).  The heading Laboratory Data was added.

Line 35 (Page 6).  Alternative:  I.V.s.

Line 38 (Page 6).  The hemoglobin value of twelve six is written as 12.6.

Line 3 (Page 7).  Alternative:  7900.

Line 7 (Page 7).  The heading Laboratory Data was added.

Line 10 (Page 7).  The white count value eight point three thousand can be written 8.3 or 8300.

Line 10 (Page 7).  Translate the slang H&H as hemoglobin and hematocrit, and change the singular verb was to were for plural agreement.