Sample Dilutions
Patient samples may require dilution in order to be analyzed correctly. Most procedures are set up with a limited concentration range. Some procedures start with a set dilution such as 1 10. As was discussed earlier with reagent dilutions, dilutions are composed of a certain amount of concentrated sample and a certain amount of diluent mixed together to make a diluted sample. These types of dilutions are usually expressed as a fraction or ratio rather than with units of concentrations. A...
Tests For Liver Function
The clinical laboratory offers several tests for the assessment of liver function. The enzymes alkaline phosphatase, ALT, AST, GGT, and 5'-nucleotidase are helpful in the assessment of the proper functioning and inflammatory status of the liver. Because the liver is the site for metabolism of carbohydrate, protein, and lipids, as well as for the synthesis of many proteins, the conjugation of bilirubin, and detoxification of drugs and other substances, the liver may be assessed by measurement of...
Growth Hormone
Disorders of Growth Hormone Secretion Case Scenario 11-3. Pheochromocytoma A Red-Haired Woman With a Taste for Bananas ADRENAL MEDULLARY HORMONES DISORDERS OF ADRENAL MEDULLARY HORMONES Pheochromocytomas Neuroblastomas LABORATORY TESTING FOR ADRENAL MEDULLARY DISORDERS Case Scenario 11-4. Neonatal Hypothyroidism Repeat Thyroid Testing on a Baby ROLE OF ENDOCRINE GLANDS IN THYROID FUNCTION Thyroid-Stimulating Hormone Pituitary Hormone Thyroid Hormone Metabolism Hypothyroidism Case Scenario 11-5....
Case Scenario 111
Type 2 Diabetes With Cardiac Risk Mildred Dodge, the Bonbon Eater Apolipoprotein A Deficiency The Jogger Congestive Heart Failure Joe Returns Silent Myocardial Infarction Woman at Risk Medication Toxicity Age-Related Drug Distribution The Clot Thickens Joe Returns Again Arterial Blood Gas Collection and Specimen Handling The Case of the Pink Patient With a Dark Blood Sample Chronic Bronchitis Blue Bloater or Pink Puffer Patient Acute Respiratory Failure Pain Medication Made Things Worse...
Test Methodology 103 Schilling Test
The Schilling test is a test for vitamin B12 absorption. The test requires the cooperation of both the laboratory and the nuclear medicine department. The test is used to differentiate the three main causes of vitamin B12 deficiency dietary deficiency, malabsorption of B12, and pernicious anemia. The Schilling test is a two-step procedure. If results in the first step indicate normal absorption, there is no need to perform the second step of the test. The patient must be fasting. The patient...
Test Methodology 67 Osmolality Measurement
Osmometry measures differences in the colligative properties of solutions. In a freezing point depression osmometer, a thermistor probe and stirring mechanism come in contact with the sample, which is supercooled to approximately -10 C, which is below the freezing point of the sample. A stirring wire vibrates to initiate freezing to a slush stage, and the heat of fusion warms the solution, causing equilibrium in temperature between freezing and thawing state. Variable resistance is measured,...
Case Scenario 66
Hyperkalemia Due to Hemolysis The Difficult Venipuncture The technologist had difficulty in obtaining blood from the 75-year-old female dialysis patient. After several attempts, the sample slowly filled a heparinized collection tube two-thirds full and then stopped filling. The needle was withdrawn, and the sample was gently but thoroughly mixed and labeled. This sample was injected into the bedside multianalyzer. The potassium was 6.1 mmol L and creatinine was 3.8 mg dL, but all other...
Test Methodology 41 Glucose
Current procedures that measure glucose use enzymatic methodology. The Reaction Enzymatic Method Three enzymatic approaches to the measurement of glucose have been explored. Enzymatic methods are specific for glucose. The hexokinase method is the reference method for glucose. The method involves two coupled reactions Glucose ATP hexoki nase- Mg2 G6PO4 ADP G6PO4 NADP G6PD gt 6-phosphogluconate NADPH H The increase in absorbance of NADPH at 340 nm is measured as directly proportional to glucose....
The Team Approach Qbr
When critical results are obtained for arterial blood gases, it is important to quickly verify that there are no errors and then communicate the results to the patient's nurse and or physician. Many laboratories have a logbook to record the time, date, patient name and identification number, result, who called, and to whom the result was given in addition to the usual reporting through a laboratory information system. daily analysis of quality control samples and periodic internal and external...
Test Methodology 34 Verification Of Pipette Calibration
The following spectrophotometric procedure is used to verify calibration of to deliver transfer or measuring micropipettes that deliver volumes up to 1000 L. This is an example of the use of p-nitrophenol in spectrophotometric verification of the calibration of a 10- L pipette. 1. All glassware should be cleaned, rinsed with distilled water, and dried. 2. Reagents required around 1.0 L of 0.01-mol L NaOH and 100 mL of 105-mg dL p-nitrophenol PNP . Dissolve 105 mg of high-purity PNP in deionized...
References
1. Kazmierczak SC Laboratory quality control Using patient data to assess analytical performance. Clin Chem Lab Med 2003 41 617-627. 2. Riebling N, Tria L Six Sigma project reduces analytical errors in an automated lab. MLO Med Lab Obs 2005 37 6 20, 22-23. 3. Montoya ID Assessing the practice of laboratory medicine. Clin Lab Sci 2004 17 2 66-67. 4. Seamark D, et al Transport and temperature effects on measurement of serum and plasma potassium. Scand J Clin Lab Invest Suppl 1996 224 275-280. 5....
Test Methodology 63 Urinary Protein
Because the concentration of protein in urine is less than the concentration in blood, more sensitive methodology must be performed to measure the concentration of urine proteins than of serum proteins. Several methods exist for the measurement of urinary protein. Turbidometric Protein may be precipitated with sulfosalicylic acid, trichloroacetic acid, or benzethonium chloride. The turbidity of the precipitate is measured photometrically. Dye binds to amino groups the resulting color change is...
Clinical Correlation Osf
Reye's syndrome is a metabolic disorder associated with fatty deposits of the liver and impaired production of urea through the ornithine cycle, causing encephalopathy. Reye's syndrome is a metabolic disorder associated with fatty deposits in the liver and impaired production of urea through the ornithine cycle, causing encephalopathy. Figure 7-7 depicts the ornithine cycle. Reye's syndrome is more frequently associated with viral disease of children, especially when treated with medications...
Why Women And Men Experience Different Risk For Heart Attacks
The Food and Drug Administration FDA and American Heart Association suggest that women are protected from heart attacks due to lipid plaque before they reach menopause. Estrogen levels in younger women are typically a factor causing them to maintain high levels of HDL in most situations. Once menopause occurs, women experience a reduction in HDL as their estrogen levels decline. Post- menopausal women are at the same risk for coronary artery disease and heart attack as men, particularly if they...
Analytical Variations in POC Blood Gas Analyzers
Some analyzers may not have temperature control devices, so samples must be analyzed immediately while at 37 C. This generally isn't a problem unless the patient has a high fever or recently received cooling intervention in surgery. Some POC analyzers are more sensitive to clots, which easily disable the analysis. Since the specimen is collected and analyzed immediately, some nonlaboratory personnel do not recognize the importance of properly mixing the syringes or capillary tubes in order to...
The Team Approach 1
Communication is an important component of processing laboratory specimens and handling specimen problems. It is important to have clearly written policies for specimen rejection and to inform those who provide inadequate specimens of these policies. Delays in testing must also be communicated. 50 Chapter 2 QUALITY ASSESSMENT Case Scenario 2-3 Specimen Transport Delay The Missing Glucose Follow-Up A physician had called to determine the morning glucose result for a patient who is diabetic. The...
The Team Approach Cxs
Laboratory analysis contributes objective information for the assessment of cardiac function. The electrocardiogram ECG or EKG produces another form of objective information. The tracings of the ECG represent electrical current as it passes through the heart muscle, causing contraction. Each lead of the ECG provides a tracing of the electrical current as it passes through a different plane of the heart. Cardiac damage, such as that caused by an AMI, produces areas of dead muscle cells that do...
Info Ihe
TEST METHODOLOGY 6-1. CREATININE continued Serum, plasma, and urine may all be measured by the Jaffe reaction. Enzymatic approaches to the measurement of creatinine have also been explored. Crea-tininase, creatinase, and creatinine deaminase have all been used to produce a measurable product that reflects creatinine concentration. Reactions are coupled with enzymatic reactions that can be measured spectrophotometrically, such as NADH to NAD or H2O2 to H2O. Serum, plasma, and urine may be...
History Of Measurement In The Laboratory
The application of biochemical testing for medical testing began about 100 years ago. One of the first clinical chemists, Dr. Otto Folin, developed quantitative analytical methods for urine analytes of urea, ammonia, creatinine, uric acid, electrolytes, and acidity. He also developed early blood tests, including those for ammonia and creatinine, using the Jaffe method. Dr. Folin helped to establish the clinical significance of renal function and metabolic tests and published the first reference...
The Team Approach Xst
Respiratory care therapists determine the alveolar-to-arterial A-a gradient using arterial blood gas values to assess if ventilation perfusion V Q mismatch is present. ARDS - respiratory distress syndrome of the adult acquired respiratory failure A large A-a gradient indicates the patient may have V Q mismatch, diffusion defect, or a shunt. The fraction of inspired oxygen, Po2 and Pco2, and A-a gradient can be correlated, taking into consideration conditions of barometric and water vapor...
Test Methodology 104 Fecal Fat Analysis
Normal fecal lipids consists of 60 fatty acids, 30 sterols, and 10 triacylglycerols. Increased fecal fats are clinically significant to the assessment of pancreatic insufficiency and small intestine disorders. Fecal fat is also increased in biliary obstruction. Direct measurement of fecal fat is used to establish a diagnosis of malabsorption. Steatorrhea is evidence of fat malabsorption but is not always present. Qualitative analysis for fecal fat employs fat-soluble stains, such as Sudan III...
The Biochemistry Of Disease
The clinical chemistry laboratory measures change in biochemical compounds as an indicator of health status or disease processes. Because the biochemical changes of compounds are not uniform in tissue and organs in response to disease, the measurement of selected biochemical markers can be used to monitor diseases processes as they occur in specific living cell systems. For instance, an increase in the concentration of urea nitrogen in the blood may indicate kidney failure and increased...
Test Methodology 92 Carbon Monoxide And Oxygen Saturation By Cooximetry
The principle of the most commonly used method for carboxyhemoglobin is measurement of the absorbance peaks using a co-oximeter with a tungsten lamp capable of emitting light from 690 to 300 nm and in particular for wavelengths in the 500- to 650-nm range. The monochromator is capable of selecting for 541, 555, 600, 626, and 630 nm. The specimen must contain hemoglobin in order to quantify the percentage of carboxyhemo-globin compared to total hemoglobin. Whole blood that has been diluted with...
Clinical Correlation Yby
The evaluation of blood urea nitrogen BUN is a gross indicator of renal function. Damaged nephrons are unable to clear urea from the bloodstream, resulting in an increased BUN. The level of BUN is also affected by patient hydration, protein diet, and gastrointestinal bleeding. from the blood and conserving, or reabsorbing, those chemicals that are needed for adequate metabolism. The kidneys maintain the balance of plasma constituents, while excreting those substances that are no longer needed...
FirstOrder and ZeroOrder Enzyme Kinetics
First-order kinetics is described in the following manner as substrate concentration increases, the rate of product formation increases hyperbolically as it combines with available enzyme and, thus, rate of product formation depends on both substrate and enzyme concentration. Zero-order kinetics is described as enzyme activity at maximum velocity Vmax due to excess substrate concentration. Increasing Figure 1-7. Michaelis-Menton curve substrate concentration versus rate of product formation....
Objectives Tkp
Upon completion of this chapter, the student will have the ability to Discuss common preanalytical errors resulting from improper specimen collection and handling and commonly encountered sources of interference in ammonia, bilirubin, total serum protein, albumin, alkaline phosphatase, alanine transaminase, and other liver enzyme analyses. Explain the role of quality control results in liver enzyme analysis. Describe the principles of alanine and aspartate transaminase, alkaline phosphatase...
Info Sqi
accuracy tudvdumefromp ette x 10o expected or nominal volume precision standard deviation x 100 mean volume 1.86 Na mmol L glucose mg dL 18 urea N mg dL 2.8 9 protein fraction X total protein g dL protein fraction g dL
Test Methodology 82 Troponin I
Troponin I is a contractile protein along with other troponin proteins found within muscle fibers, including cardiac myofibrils. Cardiac troponin I cTnl has unique specificity to cardiac muscle and is released shortly after cardiac muscle damage. It can be measured in the serum for 1 to 14 days after an AMI with a high degree of sensitivity and specificity. Levels of cTnI above the reference range or medical decision limit reflect irreversible heart muscle damage. The common principle of...
Info Nih
tared - adjusted a scale to zero, such as negating the mass of an empty vessel so that only the mass of an unknown is displayed Vibrations, air currents, extraneous dirt, and poor centering of the balance should be considered first as possible problems when a balance shows inaccurate or imprecise readings. using the gravimetric method, relating the mass of liquid dispensed by the pipette to its volume. There are two main types of balances mechanical and electronic. Mechanical scales work by a...
Bilirubin Metabolism
Bilirubin is a degradation product of the heme portion of hemoglobin. Heme is degraded in cells of the reticuloendothelial system, mainly the spleen. The proto-porphyrin ring of the heme is opened to the biliverdin form and iron is released. Biliverdin is reduced to produce the yellow-pigmented molecule bilirubin. The bilirubin molecule, a tetrapyrole, has low solubility in water or plasma. When it is released into blood, it is bound to albumin for transport. Covalently bound bilirubin is...
Info Bdk
Laboratory results should be confirmed before reporting them out, particularly if results don't correlate well with other laboratory results or with earlier results of the same analyte, known as a delta check. Physiological changes and specimen integrity should also be considered. There should also be systemic consideration of all samples under analysis in one run or time period.23 when there is a high amount of osteoblastic activity cells rebuilding bone . ALP levels of 10 to 25 times normal...
The Team Approach Rog
In a clinical setting, nonlabora-tory personnel may collect and deliver urine and blood samples. Specimen collection and handling guidelines, as established by the laboratory, must be clearly communicated to all parties involved in the specimen collection process. Urine samples must be collected in the properly labeled container, sealed, and delivered to the laboratory for testing in less than 2 hours, or 8 hours if refrigerated. Unpreserved urine samples may become overgrown with bacteria,...
Test Methodology 36 Centrifuge Maintenance Procedure
Weekly or biweekly depending on usage Clean interior components with soap and water followed by freshly made 10 v v bleach solution, including sample buckets. Wearing protective gloves, wipe interior sides and bottom, taking care when removing broken pieces of glass. TEST METHODOLOGY 3-6. CENTRIFUGE MAINTENANCE PROCEDURE continued Monthly Place two equally balanced containers into the centrifuge, cover, and operate at the most commonly used speed, listening for unusual vibrations. Check the...
Collection And Handling Of Arterial Blood Gases
The specimen for blood gases and pH should be arterial or arterialized capillary blood collected in heparinized plastic containers including syringes and capillary tubes. Ail air bubbles should be removed, and the needle replaced or the ends of the capillary tube fitted with a tight-fitting cover. Air bubbles frequently form during syringe collection but must be expelled before mixing the specimen. The container should hold the correct amount of heparin 0.05 mg heparin mL blood and, after blood...
Info Hoq
The glucose, blood urea nitrogen BUN , and creatinine results in the initial sample, likely contaminated with IV solution, were approximately one-third lower than the values that were obtained from the redrawn sample. The sodium and chloride results were higher in the first sample due to saline contamination from the IV fluid. Total protein and albumin can also be considerably decreased when measured in specimens contaminated with IV fluid. The saline IV fluid used in this case has a higher...
Hemolysis Why Is the Potassium Level So High Today
A physician called the laboratory to inquiry about a specimen collected from his patient. The plasma potassium concentration had been reported as 5.9 mmol L. This value was abnormally high when compared to the reference range 3.5 to 4.5 mmol L for potassium. The physician was concerned that hemolysis had falsely elevated the potassium result. The technologist checked the sample and assured the physician that there were no visible signs of hemolysis. tourniquet - band used on arm to cause the...
Immunoassay Techniques
An immunoassay is an analytical method that uses antibodies or antigens as reagents to measure specific chemicals, or analytes. The immunoassay has been in use for over 30 years. Results from immunoassays are the basis for many critical human health decisions involving detection of viruses and their antibodies, therapeutic drug monitoring, and screening for drugs of abuse. Over 70 clinical analytes are tested by immunoassay. The immunoassay technique is the basis for many home tests, and even...
Renal Tubular Acidosis
Renal tubular acidosis RTA is a tubular defect of acid-base regulation. This condition is characterized by alkaline pH of the urine with acidic blood plasma pH, which causes depletion of potassium and bicarbonate ions. Typically, secondary muscle and bone weakness occurs due to the profound electrolyte and mineral imbalance, especially from hypokalemia. Renal tubular acidosis can be classified as a primary disorder, such as a proximal tubular defect associated with Fanconi's syndrome or...
H 1
HPO34HSO24 2 Org. acidf Protein NC NC No Change SL Slight Increase 4- Decrease Increased Anion Gap with Increased Concentration of Organic Acid Figure 6-4. Diagram representing balance of cations and anions. the ions with only about 15 mmol L contributed by unmeasured anions. The anion gap represents those unmeasured anions that are present in body fluids providing electrolyte balance and neutrality, such as lactate, sulfates, phosphates, ketones, organic acids, and ionized proteins. The use of...
Calculations in Arterial Blood Gas Analysis
Given arterial pH and Pco2, the formula to solve for bicarbonate is derived as follows pH pKa log HC03- Pco2 X 0.0301 pH - pKa log HCO3 H2CO3 inv. log pH - pKa HC03- H2C03 inv. log pH - pKa X H2CO3 HCO3- For example, calculate HCO3- given pH 7.50 and Pco2 of 30 mm Hg. 7.50 6.1 log HC03- 30 X 0.0301 7.50 6.1 log HC03- 0.9 1.4 log HC03- 0.9 inv. log 1.4 HC03- 0.9 25 HC03- 0.9 25 X 0.9 HC03- 23 mmol L Base excess BE is best determined from a nomogram or the van Slyke equation. Case Scenario 9-1...
Analysis Of Oxygenation
Oxyhemoglobin O2Hb can be measured using a co-oximeter, a dedicated spectrophotometer. Oxyhemoglobin exhibits peak absorbance at 585 and 540 nm, while deoxyhemoglobin HHb peaks at 594 nm. Total hemoglobin is generally a sum of oxyhemoglobin and deoxyhemoglobin. The formula used to calculate SO2 is the proportion of oxyhemoglobin within the total hemoglobin concentration. In this formula, c represents concentration and Hb represents hemoglobin. Total hemoglobin SO2 cO2Hb cO2Hb Errors in this...
pH and pOH Calculations
Concentration of a strong acid can also be presented in a way that represents the ionization of the hydrogen ions in solution, or the potential. Thus, pH is the potential - force of electrical potential of H as it relates to the negative, or inverse, log of the hydrogen ion con- activity in volts centration, expressed as H , in mol L. Mathematically, the pH of a strong acid is equal to the inverse log of the hydrogen ion molar concentration since it completely dissociates to hydrogen ions when...
Test Methodology 42 Ketones
This method uses a sodium nitroprusside reagent that also contains glycerine, disodium phosphate, and lactose. Sodium nitroprusside acetoacetic acid acetone lavender color False-positive reactions are due to medications such as L-dopa, methyldopa, 8-hydroxyquinoline, and phenolphthaleins. False-negative reactions can occur due to exceeding linearity of reaction. Dilutions of suspected highly positive results are required to verify actual reaction. False-negative reactions are also due to...
Info Gyc
most serum enzymes must be considered. An alternative to clotted tubes that are held for later retesting is the use of serum separator tubes. These contain an inert polymer that moves between the clotted blood cells and the serum during cen-trifugation. This gel barrier can prevent release of intracellular constituents for several hours. However, gel barriers can't be used for therapeutic drug monitoring since they can interfere with specimen testing. Separated blood, serum, or plasma is...
Medical Decision Limits
true positive - result at or above the decision limit in a patient who has the disease false positive - result at or above the decision limit in a patient who does not have the disease true negative - result below the decision limit in a patient who does not have the disease false negative - result below the decision limit in a patient who has the disease Along with determining the reference ranges to correlate with absence of disease, it is also helpful for physicians to have a cutoff value to...
Info Qkc
Voltammetry is an electrochemical technique similar to polarography except that electrical potential is varied over time. There is typically a working reference electrode and direct current is applied to it initially as a large negative potential is generated. Metal ions are reduced at the surface of the reference electrode. This causes them to be strongly attracted to the surface of the electrode. In the next step, the direct current is applied as a large linear positive potential, causing the...
Info Imn
Case Scenario 4-1 Diabetes Mellitus Type 1 The Emergency Department continued regimen. During Brandon's admission for treatment of hypertension in the previous year, the following additional lab results were obtained Serum creatinine mg dL 0.5 0.5-1.0 Creatinine clearance mL min 1.73 m2 183 93-131 Urine albumin excretion rate g min 240 lt 20 Blood pressure mm Hg 132 90 120 80 Hypertension, defined as blood pressure greater than or equal to 140 90 mm Hg, is a common complication of diabetes....
Case Scenario 67
Pseudohyponatremia A Problem With Analysis While analyzing samples in the STAT lab, the technologist noted a creamy tomato soup appearance of a heparinized whole blood specimen. The specimen was accompanied by a requisition for electrolyte analysis from the emergency department. The results of laboratory testing are listed below. Test Patient Reference Ranges Sodium mmol L 135 136-145 Potassium mmol L 3.6 3.5-5.1 Chloride mmol L 99 98-107 Bicarbonate mmol L 24 22-28 Anion gap mmol L 16 10-20...
Correlation of POC Blood Gas Analyzer With BenchTop Instrument Are We Comparing
The new clinical chemistry technical supervisor is asked to evaluate the use of the Instrumentation Laboratory IL GEM Premier 3000TM point-of-care blood gas analyzer for use by the respiratory care department and by personnel in surgery, and also to compare its patient results to those from the Radiometer ABLTM bench-top blood gas analyzer. The new analyzer also may be used as a backup instrument when the laboratory analyzer is inoperable. Prior to performing a method evaluation of the new...
The Team Approach Jtf
Routine urine handling requires properly labeled and covered containers but usually doesn't require protection from light. If porphyrinogens or porphyrins are suspected, the specimen should also be protected from light, and communication with nursing staff may be necessary to get a light-protected urine sample. Case Scenario 5-3 Acute Variegate Porphyria Darkening Urine Samples in the Laboratory continued TEST METHODOLOGY 5-3. URINE PORPHYRIN, PORPHYRINOGEN, AND PORPHOBILINOGEN continued Figure...