CLS - Clinical Chemistry

Which of the following statements regarding the L/S ratio is TRUE? a. A ratio of 2:1 or greater usually indicates adequate pulmonary surfactant to prevent respiratory distress syndrome (RDS) b. A ratio of 1.5:1 indicates fetal lung maturity in pregnancies associated with diabetes mellitus c. Sphingomyelin levels increase during the 3rd trimester causing the L/S ratio to fall slightly during the last two weeks of gestation d. A phosphatidylglycerol (PG) spot indicates the presence of meconium in the amniotic fluid

a. A ratio of 2:1 or greater usually indicates adequate pulmonary surfactant to prevent respiratory distress syndrome (RDS) Until about 32-33 weeks of gestation, the concentration of these two substances are quite similar; thereafter the concentration of lecithin increases significantly compared with the relatively constant concentration of sphingomyelin. In the absence of complications, the ratio of these two components reaches 2.0 at about 35 weeks gestation. Infants delivered after attaining an L/S ratio of 2.0 or higher rarely develop RDS. This value of 2.0 has become the commonly accepted standard value indicating maturity in the fetus of a non-diabetic woman.

In a standard electrophoretic separation, what zone appears first (anodal end) on the densitometric pattern? a. Albumin b. a1-globulins c. a2-globulins d. B-globulins

a. Albumin

Calcium and phosphorus levels were determined for a 4-year-old patient as follows: Ca - 14 mg/dL Phosphorus - 1 mg/dL These results are MOST compatible with a. Hyperparathyroidism b. Renal failure c. Rickets d. Hypervitaminosis

a. Hyperparathyroidism The calcium is elevated. The main cause of hypercalcemia is almost always due to hyperactivity in one or more of the parathyroid glands, which regulate calcium. The phosphorus level is decreased. High calcium levels usually result in decreased phosphorus levels.

When measuring enzyme activity, if the instrument is operating 5*C lower than the temperature prescribed for the method, how will the results be affected? a. Lower than actual b. Higher than actual c. Varied, showing no particular pattern d. No effect

a. Lower than normal The activity is strongly affected by changes in pH and temperature; therefore, it would be predicted that a lower temperature inside of the analyzer would lead to lower enzyme activity.

Which of the following immunosuppressive drugs has been associated with thrombus formation in patients with toxic levels? a. Tacrolimus b. Cyclosporine c. Sirolimus d. Mycophenolic acid

a. Tacrolimus

A CSF glucose value is 62 mg/dL. What would you estimate the serum glucose? a. 65 mg/dL b. 93 mg/dL c. 120 mg/dL d. 180 mg/dL

b. 93 mg/dL CSF glucose is roughly estimated to be about 2/3 of the serum glucose level in mg/dL. Therefore: 62 = 2/3 x (serum glucose) serum glucose = 92 mg/dL

The tumor marker associated with ovarian cancer is a. CA15-3/CA27.29 b. CA-125 c. PSA d. CEA

b. CA-125 CA-125, a mucin-like glycoprotein, is expressed on the surface of the main body cavity, coelomic, epithelium, and human ovarian carcinoma cells. CA 125 is relatively more sensitive in low-stage ovarian cancer. This classic tumor marker is elevated in cancer, and benign disease of various organs, e.g., pelvic inflammatory disease, endometriosis, but is most useful in the diagnosis and monitoring of ovarian and endometrial carcinomas.

After complaining to her physician about persistent pelvic pain and abdominal pressure, Mrs. Smith, had laboratory testing ordered. Since her physician would like to rule-out ovarian cancer, which of the following assays would be most helpful? a. CEA b. CA125 c. CA19-9 d. PSA

b. CA125 CA125 is an antigen present in approximately 80% of ovarian carcinomas. CA125 is often elevated in patients with ovarian cancer and its concentration follows the course of the disease. It is important to note that CA125 is not completely specific for ovarian carcinomas. It can be found in increased levels in other cancers including endometrial, pancreatic, lung, breast, and colon cancer, along with other conditions such as pregnancy.

The most common methods for measuring bilirubin are based on the reaction of bilirubin with a. Methyl alcohol b. Neural salts c. Bilirubin oxidase d. Diazo reagent

d. Diazo reagent

In patients with suspected primary hypothyroidism associated with Hashimoto's thyroiditis, one would expect the following laboratory test results: T4 ____? TSH ____? TRH stimulation ____? a. Increased, decreased, increased b. Decreased, increased, increased c. Increased, decreased, decreased d. Increased, increased, decreased

b. Decreased, increased, increased In Hashimoto's thyroiditis antibodies react against proteins in the thyroid gland, causing gradual destruction of the glad itself and making the gland unable to produce the thyroid hormones the body needs.

In hemoglobin synthesis, which enzyme is responsible for adding iron in the last step? a. ALA Synthase b. Ferrochelatase c. PBG Synthase d. Protoporphyrinogen oxidase

b. Ferrochelatase Ferrochelatase is the enzyme responsible for adding iron into the porphyrin ring in the final step of heme synthesis.

Which of the following is the principle for the biuret method for total protein analysis? a. Digestion of protein; measurement of nitrogen content b. Formation of violet-colored chelate between Cu2+ ions and peptide bonds c. Globulins are precipitated in high salt concentrations d. Proteins seperated based on electric charge

b. Formation of violet-colored chelate between Cu2+ ions and peptide bonds a is the principle for the Kjeldahl method for total protein measurement. c is the principle for salt precipitation and it is considered an albumin method, not a total protein method. d is the principle for electrophoresis

An increase in total bilirubin with a normal conjugated bilirubin is most likely indicative of a. Acute liver disease b. Hemolytic disease c. Post-hepatic jaundice d. Obstruction

b. Hemolytic disease As RBCs breakdown increases, the iron is removed and the heme portion is catabolized to unconjugated bilirubin. However, before bilirubin can be excreted, it needs to be conjugated in the liver. Therefore, an increase in unconjugated with a normal conjugated fraction indicates a hemolytic event rather than an acute liver disease.

When considering therapeutic drug monitoring (TDM), what is the definition of bioavailability? a. The relative proportion between the circulation and the tissues b. The fraction of the administered dose eventually reaches its site of action c. The variations in drug metabolism as related to genetics d. The metabolic generation of a therapeutically active metabolite

b. The fraction of the administered dose eventually reaches its site of action a is the drug's distribution c is examined in the discipline of pharmacogenomics d is an enzymatic process referred to as biotransformation

If a disease or disorder causes serum binding proteins (such as albumin) to decrease, what may occur if the dose of a highly protein-bound drug with a narrow therapeutic window is not adjusted? a. The patient may not realize a therapeutic benefit (low free drug fraction) b. The patient may experience toxic affects (high free drug fraction) c. The serum level of the drug will most likely remain in the therapeutic range d. Not enough information is provided to determine the effect of the drug on the patient

b. The patient may experience toxic affects (high free drug fraction) If serum protein levels fall, as can occur in liver failure or nephrotic syndrome, less protein (specifically albumin) will be available for drug binding; a subsequent dose may produce a toxic concentration of the free drug.

The National Heart, Lung, and Blood Institute (NHBLI) and American Heart Association (AHA) have created a set of parameters to define the presence of metabolic syndrome. Select the set of laboratory assays that are utilized in the NHLBI and AHA criteria for metabolic syndrome diagnosis. a. LDL-C, triglycerides, HDL-C, and fasting blood glucose b. Fasting blood glucose, triglycerides, insulin, and VLDL c. Fasting blood glucose, triglycerides, HDL-C d. Fasting blood glucose, triglycerides, HDL-C, VLDL

c. Fasting blood glucose, triglycerides, HDL-C There are 5 basic parameters described below as metabolic risk factors. A patient must have at least 3 of the 5 risk factors to be diagnosed with metabolic syndrome. 1. a large waistline. In women, >=35in; in men, >=40in 2. High triglyceride level, >=150 mg/dL 3. High fasting blood glucose, >=100 mg/dL 4. Low HDL cholesterol. In women, <=50 mg/dL; in men, <=40 mg/dL 5. High blood pressure, that is >= 130/85 mm Hg

Patients who develop severe sepsis or septic shock commonly have _____ plasma lactate values. a. Decreased b. Normal c. Increased d. Markedly decreased

c. Increased This is considered Type B lactic acidosis and is of metabolic origin. Other causes for Type B lactic acidosis include diabetes mellitus, leukemia, liver or renal disease, and poisoning with ethanol, methanol, or salicylate.

Metabolic acidosis is characterized by a. Increased pCO2 b. Hypoventilation c. Low pH d. High pH

c. Low pH Metabolic acidosis results from either 1) accumulation of abnormal levels of organic acids, often secondary to diabetic ketoacidosis, or lactic acidosis 2) excessive loss of bicarbonate as in sever diarrhea 3) reduced excretion of acids as in renal failure All these conditions result in a decrease in pH. The body compensates by hyperventilating and lowering pCO2 to restore normal pH, resulting in a compensated or partially compensated metabolic acidosis.

A male patient's urea nitrogen value is 15 mg/dL and his creatinine is 5 mg/dL. If this patient is not undergoing dialysis, what conclusion would you draw from these results? a. The patient's laboratory results are normal b. The patient is in the early stage of renal disease c. One of the values is in error d. The patient has suffered muscle deterioration

c. One of the values is in error The patient's urea nitrogen is within the normal range while the creatinine is about 5 times the upper normal range. Gross elevations in creatinine are almost always accompanied by elevations in urea nitrogen when there is kidney impairment. Urea nitrogen to creatinine ratio is normally 10:1 to 20:1, in our case it's 3:1 which is abnormally low. Therefore, either the urea nitrogen or creatinine value, in this case, is incorrect. Both tests should be repeated.

Human chorionic gonadotropin (hCG) is used in the determination of a. liver function b. fetal maturity c. pregnancy d. steriod levels

c. pregnancy hCG is a hormone produced in pregnancy that is made by the developing embryo and later produced by the placenta. Its role is to maintain progesterone production that is critical for a healthy pregnancy.

All cells can synthesize heem; what two organs are the main sites of hemoglobin synthesis for the body? a. Liver and spleen b. Spleen and bone marrow c. Bone marrow and thymus d. Bone marrow and liver

d. Bone marrow and liver

What is the term used to describe inadequate blood supply that decreases availability of oxygen to the myocardium? a. Acute myocardial infarction (AMI) b. Angina c. Congestive heart failure (CHF) d. Myocardial ischemia

d. Myocardial ischemia AMI - cardiac tissue death due to lack of oxygen caused by obstruction of circulation Angina - chest pain caused by an inadequate supply of oxygen to heart myocardium CHF - a clinical syndrome caused by heart disease, represented by abnormal sodium and water retention and breathlessness, usually resulting in edema

Ionized calcium is currently most commonly measured using which of the following methods? a. flame photometry b. color complex formation between calcium and o-cresolphthalein c. atomic absorption d. calcium ion selective electrodes

d. calcium ion selective electrodes A calcium ISE has a PVC membrane, which is impregnated with an organic molecule that selectively binds and transports Ca++ ions, and contains an internal solution with a fixed concentration of calcium chloride - added to the KCl / AgCl solution of the internal reference system.

The bioavailability of an oral drug refers to the a. availability for therapeutic administration b. ratio of protein-bound to free drug c. amount of drug transformation d. fraction of the drug that is absorbed into the systemic circulation

d. fraction of the drug that is absorbed into the systemic circulation The bioavailability of a drug is calculated by comparing the area under the plasma concentration-time curve of an equivalent dose of the intravenous form and the oral form of the drug. For oral drugs to be effective, bioavailability should be greater than 70%