Chemical Analysis Flashcards
PH
Principle
Reagents
Misc Info
Principle: double indicator
Reagents: methyl red and bromthymol blue
Misc Info
Normal 5.0 – 8.0
Protein
Principle
False pos and neg interferences
Misc Info
Principle: protein error of indicators
Reagents: tetrabromphenol blue
False Pos: drugs, highly buffered or alkaline urine
False Neg: presence of protein other than albumin
Misc Info: Normal: Negative
Glucose
Principle
False pos and neg interferences
Misc Info
Principle: double sequential enzyme reaction
Reagents: Chemstrip tetramethylbenzidine
Multistix: Potassium iodide
False Pos: strong oxidizing agents; bleach
Peroxide contaminants
False Neg: ascorbic acid -improper storage
Misc Info: Normal: Negative
Ketones
Principle
False pos and neg interferences
Misc Info
Principle: Nitroprusside rxn
Reagents: Nitroferricyanide
Chemstrip-glycine
False Pos: Pigmented urine, levodopa metabolites
False Neg: improper storage
Misc Info: Normal: Negative
Blood
Principle
False pos and neg interferences
Misc Info
Principle: Pseudoperoxidase activity of heme moiety
Reagent: tetramethylbenzidine
False Pos: Peroxidase, menstruation
False Neg: ascorbic acid, nitrites, improperly mixed spec
Misc Info: Normal: Negative
Bilirubin
Principle
False pos and neg interferences
Misc Info
Principle: Diazo coupling rxn
Reagent: Chemstrip: dichlorobenzenediazonium tetrafluroboroate.
Multistix dichloroaniline diazonium salt
False Pos: Drugs
False Neg: ascorbic acid, high nitrite concentrations,
improper storage with exposure to light
Misc Info: Normal: Negative
Urobilinogen
Principle
False pos and neg interferences
Misc Info
Principle: azo coupling rxn - chemstrip
modified Ehrlich rxn - multistix
Reagent: 4 methoxybenzene diazonium fluorborate -
p-dimethylaminobenzaldine - multistix
False pos: Drugs, beets
False neg: formalin, improper storage, old specimen
Misc Info: Normal: < 1mg/dL
Nitrate
Reagent
False pos and neg interferences
Misc Info
Reagents: Chemstrip: sulfanialamide
aromatic compound
Multistix: p-arsanilic acid aromatic compound
False pos: drugs, beet ingestion, improper storage
False Neg: ascorbic acid,
Misc Info: Normal: Negative
Leukocyte Esterase
Principle
False pos and neg interferences
Misc Info
Principle: esterase activity
Chemstrip: indoxylcorbonic acid ester
Multistix: pyrroleaminoacid ester
False Pos: drugs, beet ingestion, vaginal contamination. formalin
False Neg: increase conc of glucose, oxidizing agents, tetracyclines
Normal: Negative
Specific gravity
Principle
False pos and neg interferences
Misc Info
Principle: Polyelectrolyte on strip
Reagent: Chemstrip: ethylenglycol-bistetra acetic acid
Multistix: polymethylvinul ether malic acid
False Pos: High conc. Of protein, ketoacidosis
False Neg: Glucose and urea
Misc Info: Normal: 1.000 – 1.030
Ictotest
Principle and Purpose
Principle: Bilirubin glucoronide (aromatic compound) plus a Diazonium salt gives a azobilirubin (azodye brown/purple)
Purpose: Bilirubin
SSA
Principle and Purpose
Principle: Proteins denature in SSA, turbidity is observed
Purpose: Low molecular weight proteins
Microalbumin
Principle and Purpose
Principle: Immunodip, Micral tests strips, CLINITEK Microalbumin test strips, Creatinine, Multistix PRO test strips
Purpose: Minute amounts of albumin
Hoesch Test
Principle and Purpose
Principle: 10 parts (2 mL) Ehrlich’sreagent and 1 part (2 drops) urine in acidic urine, will develop red/pink if porphobilinogen is present
Purpose: Porphobilinogen
Benedicts Test
Principle and Purpose
Principle: Reducing substance + cupric sulfate cuprous oxide (colored)
Purpose: Tests for reducing carbohydrates such as galactose, lactose, fructose, glucose.
Acetest Test
Principle and Purpose
Principle: Reagent:nitroprusside
Purpose: Ketones
Discuss the care and storage of reagent strip and how often QC is performed.
Store reagent strip in the original container at room temperature, keep out of light, once opened they can only be used for six months.
QC needs to be performed daily on both a positive (usually purchased) and negative(can either be purchased or DI water) control
Explain isothenuria and what this diagnosis indicates for the patient.
Isothenuria is a urine that has a fixed specific gravity of 1.010. It is the result of the kidneys inability to concentrate urine. The urine has the same specific gravity as plasma. Meaning the urine is an indication of end stage renal disease and is often associated with nocturia.
Discuss the clinical significance of urine specific gravity results.
1.000 - water, impossible
1.001-1.009 - associated with increase water intake considered dilute urine
1.010-1.025 - normal specific gravity
1.025-1.035 - assocaited with decreased water intake, dehydration, or profuse sweating
>1.040 - indicated iatrogenic substances, impossible
Correlate the clinical significance with pH results seen on the reagent strip.
<4.5 impossible
- 5-6.9 Acidic urine-diet high in proteins, metabolic and respiratory acidosis, UTI, and medications.
- 0-7.9 Alkaline or basic urine-diet rich in fruits and vegetables, metabolic and respiratory alkalosis, UTI, and medications.
> 8.0 impossible indicates iatrogenic substances
List two other methods of testing the urine pH.
The pH meter and pH test paper
What term best describes Red Blood Cells present in the urine?
Hematuria. The term hemoglobinuria is the presence of hemoglobin in the urine. The term myoglobinuria is the presences of the protein that carries oxygen to the muscles
Hematuria
Pink/Red/Brown /Cloudy
Yellow
Spotted positive
Hemoglobinuria
Pink/Red/Brown clear
Red
Positive
Myoglobinuria
Pink/Red/Brown clear
Yellow
positive
Describe why it is important to differentiate hemoglobinuria from myoglobinuria?
Myoglobinuria is toxic to kidney
What is the clinical significance of hemosiderin in a urine specimen
Indicates increase heme processing, present in paroxysmal nocturnal hemoglobinuria
Explain the methodology of the leukocyte esterase reagent pad and describe why lymphocytes are not detected by this methodology
Leukocyte esterase is an enzyme found in the azurophilic granules of the granulocytes. Lymphocytes do not contain any granules therefore are not detected by the reagent pad.
A positive nitrite test and a positive leukocyte esterase test is usually indicative of a urinary tract infection. List the organisms that most commonly cause UTI’s from the least common to the most common.
Klebsiella > Enterobacter > Proteus > E.coli
True or false a negative nitrite test will always indicate that no bacteria are present in the urine.
False there are some bacteria that do not produce the nitrate reductase enzyme and there are times when the organism has reduced the nitrates to nitrites
Pre renal: Overflow proteinuria
Proteins Present
Causes
Tests
Proteins present: Myoglobin, Hgb, Acute phase reactants, Bence Jones proteins
Causes: Muscle injury, Intravascular hemolysis, infection, MM
Tests: Reagent strip, microalbumin, SSA(Bence Jones)
Renal: Glomerular proteinuria
Proteins Present
Causes
Tests
Proteins Present: Albumin, transferrin, α-Antitrypsin, α1-
Acid glycoprotein
Causes: Primary glomerular disease, Glomerular damage secondary to other conditions, Transitory glomerular changes
Tests: Reagent Strip, Total Protein
Renal: Tubular proteinuria
Proteins Present
Causes
Tests
Proteins Present: Albumin, α2-microglobulin, α1-microglobulin,
Retinol-binding protein, β2-microglobulin, Lysozyme
Causes: Acute/chronic pyelonephritis, interstitial nephritis, Renal tubular acidosis, renal tuberculosis, Fanconi’s syndrome
Tests: Total Protein, reagent strip
Post renal: Produced by the urine or is present as a result of contamination
Proteins Present
Causes
Tests
Proteins Present: Pus, menstrual proteins, vaginal secretions
Causes: Inflammation, injury, tumor, contamination
Tests: negative
What is the normal range for protein in the urine? What is happening in the kidney if excess protein is being excreted
150 mg/24 hrs
Proteinuria is a result of increased amounts of protein being filtered and not reabsorbed or a reduction in the tubules= reabsorptive ability.
Describe how elevated levels of glucose appear in the urine?
Glucose is normally reabsorbed by the proximal renal tubules. Glucose presents in the urine as either a pre renal condition or as a result of renal damage specifically the tubules. Pre-renal conditions consist of conditions such as Diabetes Mellitus, hormonal disorders, liver disease, pancreatic disease, drugs. In these conditions plasma glucose levels exceed the renal plasma threshold of 160-180 mg/dL
Interpretation of clinitest versus dipstick glucose results:
Dipstick Clinitest Interpretation
Negative Negative -No glucose or reducing substance
Negative Positive -Reducing substance other than glucose present
Positive Positive -Glucose and possibly other reducing substance
Positive Negative -Only glucose is present
When do ketone bodies appear in urine? What are they?
Ketones are present because of increased fatty acid metabolism as a result of a person being unable to utilize carbohydrates(diabetes mellitus), insufficient consumption: starvation, alcoholism, exercise, or as a result of a loss of carbohydrates. The three ketone bodies are acetone, acetoacetic acid(AAA), beta-hydroxybutyric acid
Identify one advantage of acetest.
Can be used on samples other than urine.
Describe in detail hemoglobin catabolism. Include how the heme is broken and where the breakdown takes place
Peripheral tissue - Heme to Biliverdin to Bilirubin
Blood - Bilirubin reversibly binds to albumin forming a large soluble complex
Liver - Albumin removed and Bilirubin conjugated with glucuronic acid
Normally: All conjugated bili excreted into bile duct and go to small intestine
Abnormal: Excreted by kidneys into the urine
Intestine - reconverted to unconjugated form and reduced by bacteria to colorless urobilinogen
Classify the type of jaundice present what caused the condition and the results of the bilirubin and urobilinogen on the reagent strip.
Prehepatic
Hepatic Disorder
Posthepatic
Prehepatic - Transfusion reactions, sickle cell disease, hereditary spherocytosis, HDN, thalassemia, PA Negative Elevated
Hepatic disorder - Hepatitis, cirrhosis, genetic disorders Positive normal
Posthepatic - Gallstones, tumors, fiborosis Positive Decrease or absent
Describe the physical examination of a urine with elevated bilirubin results.
Dark yellow to amber with a yellow foam.
Can bilirubin results be reported directly from the dipstick–why or why not:
Depends upon the sensitivity of the reagent strip. The reagent strips are usually sensitive to approximately 0.5 mg/dL. The Ictotest is sensitive to approximately 0.05 – 0.1 mg/dL.
Most laboratories do not perform confirmatory tests if the reagent strip is positive, however, the Ictotest should be performed if the practitioner has specifically ordered
True or False Urobilinogen is reported as positive or negative?
False in normal hemoglobin catabolism there is always about 1mg/dL of urobilinogen present in the urine
Describe two tests used for the detection of prophobilinogen.
Hoesch test and the Watson-Schwartz test both of which use the Ehrlich reaction methodology .
Discuss the sensitivity and specificity in the identification of porphyria.
Hoesch test is sensitive to prophobilinogen levels as low as 2 mg/dL and is specific to prophobilinogen.
Watson-Schwartz can detect levels as low as 0.6mg/dL and is not specific to just prophobilinogen it also detects urobilinogen.
