ASCP Urinalysis/Body Fluids – Flashcards
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What is he major functional unit of the kidney?
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nephron
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Approximately how many nephrons are there per kidney?
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1 million
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The nephron is composed of?
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glomerulus, renal tubules
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What is a glomerulus composed of?
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capillary vessels
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What is the function of a glomerulus?
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non-selective filter of plasma substances less than 70k MW
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What substances comprise the glomerular fjiltrate?
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water, glucose, electrolytes, amino acids, urea, uric acid, creatinine, ammonia
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What is the function of the proximal tubule?
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reabsorbs water, NaCl, HCO3, K, Ca, amino acids, PO4, protein, glucose
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Glucose is a threshold substance that reabsorbs within the proximal tubule at?
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160 - 189 mg/dl or less
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What does the descending loop of henle reabsorb?
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water
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What doesn't the descending loop of henle reabsorb?
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solutes
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What does the ascending loop of henle reabsorb?
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solutes (Na, Cl, Ca, Mg)
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What doesn't the ascending loop of henle reabsorb?
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water
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What do the distal and collecting tubules reabsorb?
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Na
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What do the distal and collecting tubules secrete?
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K, NH4, H+
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Potassium ions are exchanged for what in the distal and collecting tubules?
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Na ions
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What is the rate of filtration of the glomerulus?
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120 ml/min or 1/5 of renal plasma
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What is the normal amount of urine excreted per day?
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1200 - 1500 ml/day
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Polyuria is defined as?
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greater than 2500 ml of urine excreted per day (excess urine excretion)
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What conditions can cause polyuria?
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diabetes insipidus, diabetes mellitus, diuretics, caffeine, alcohol
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Oliguria is defined as?
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less than 500 ml of urine excreted per day (decreased urine excretion)
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What conditions can cause oliguria?
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dehydration, vomiting, diarrhea, burns, perspiration
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Anuria is defined as?
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complete cessation of urination
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What conditions can cause anuria?
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kidney damage, decreased blood flow to kidneys
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Nocturia is defined as?
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increased urine volume at night?
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Urine is composed of?
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urea, uric acid, creatinine, inorganic solids (Cl, Na, K), water
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What is a metabolic waste product produced in liver from breakdown of protein?
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urea
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Aldosterone is secreted from?
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adrenal cortex
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What is the function of aldosterone?
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increases the rate of sodium reabsorption
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Arginine Vasopressin (AVP/ADH) is secreted from?
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posterior pituitary gland
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What is the function of AVP?
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reabsoprtion of water from the distal tubules
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A deficiency of AVP occurs in what condition?
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diabetes insipidus
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Erythropoietin (EPO) is secreted from?
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kidney
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What is the function of EPO?
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stimulates production of erythrocytes
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What type of urine specimen is considered ideal?
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first morning (most concentrated)
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What type of urine specimen is ideas for a bacterial culture?
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midstream clean catch
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Catheterization involves?
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inserting a catheter directly into the bladder via the urethra
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Catheterization avoids?
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external contamination (may introduce an infection though)
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Pediatric urine specimens are collected by?
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placing a plastic collection bag over the genital area (many sources of contamination associated with this collection method)
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Suprapubic aspiration specimens are collected by?
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inserting a needle through the suprapubic abdominal area directly into the bladder
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Suprapubic aspirations avoid?
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external contamination
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What are negative aspects of suprapubic aspirations?
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invasive, may introduce infection
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What is the optimal specimen collection method for bacterial cultures?
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suprapubic aspiration
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24 hour urine specimens are used for?
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quantitative urine studies
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How is the completeness of a 24 hour urine determined?
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creatinine levels (should be greater than 1.0 mg/dl)
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Urines should be analyzed within what timeframe of voiding?
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1 hour
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What values increase as a result of prolonged sitting of urine specimens?
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nitrite (bacterial growth), pH (urea is converted into ammonia), turbidity (bacterial growth/amorphous material)
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What values decrease as a result of prolonged sitting of urine specimens?
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glucose (glycolysis due to bacteria/yeast), ketones (volatization), bilirubin (exposure to light), urobilinogen (oxidation), cells/casts (lysis)
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Urines can be preserved for how long?
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24 hours
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What is the preservation method of choice for urines?
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refrigeration
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What may result if urines are preserved in a refrigerator?
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precipitation of amorphous crystals
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A fruity odor associated with urine can be attributed to the presence?
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ketones
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An ammonia-like odor associated with urine can be attributed to?
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the age of the urine (old)
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A mousy odor associated with urine can be attributed to what condition?
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PKU (phenylketonuria)
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A maple syrup like odor associated with urine can be attributed to what condition?
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maple syrup disease
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What compound gives urine its normal color?
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urochrome
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What type of urine specimen may be more on the alkaline side?
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postprandial (2 hours after eating)
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What is the typical pH of a normal urine?
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6.0
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The pH of a random urine can range from?
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4.5 - 8.0
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What can cause a urine to be cloudy?
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cells, casts, crystals, bacteria
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The presence of what substances can cause urine to appear more red?
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hemoglobin, RBCs, myoglobin, porphyrin, uroerythrin
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The presence of what substances can cause urine to appear more red-brown?
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hemoglobin, RBCs, myoglobin
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The presence of what substances can cause urine to appear more yellow-brown/amber-yellow-green?
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bilirubin, biliverdin
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The presence of what substance can cause urine to appear more yellow-orange?
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bilirubin, urobilin, pyridium (drug)
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The presence of what substances can cause urine to appear bright yellow?
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vitamin C
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The presence of what substances can cause urine to appear dark yellow?
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concentrated specimen, bilirubin, urobilin
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The presence of what substances can cause urine to appear brown-black?
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methemoglobin (oxidized RBCs), homogentistic acid (alkaptonuria), melanin
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The presence of what substances can cause urine to appear blue?
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indican (tryptophan metabolic disorder)
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The presence of what substances can cause urine to appear green/blue-green?
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old urine, psuedomonas
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The presence of what substances can cause urine to appear port wine?
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porphyrin
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The urine pH of a vegetarian is usually more?
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alkaline
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What can cause urine to become more acidic?
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metabolic or respiratory acidosis, high protein diet, cranberry juice
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Specific gravity measurements can help determine?
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the concentration and dilution function of the kidney tubules
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What is the normal specific gravity of urine?
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1.002 - 1.035
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What is the highest specific gravity value that the kidneys can concentrate?
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1.040
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Increased specific gravity values can be attributed to?
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large amounts of glucose, radio-opaque dyes (renal x-ray procedures)
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Decreased specific gravity values can be attributed to?
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diabetes insipidus
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Specific gravity is proportional to?
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color (the higher the SG the deeper the color)
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What is the defect associated with diabetes mellitus?
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decreased insulin
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What is the defect associated with diabetes insipidus?
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decreased AVP/ADH
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What symptoms are seen in both diabetes insipidus and mellitus?
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polyuria, polydipsia
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What substances are increased in the urine of an individual with diabetes mellitus?
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specific gravity, glucose, ketones
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What substances are decreased in an individual with diabetes insipidus?
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specific gravity
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Urinary measurments of glucose and ketones are normal in what type of diabetes?
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insipidus
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Refractometers measure?
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the refractive index of urine
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Corrections must be made with refractometers in the case of?
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large amounts of protein
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How do you correct a SG value higher than 1.035?
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dilute the urine specimen 1:2 with water and multiply the last 2 digits of the result by 2
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What is the principle of the measurement of protein in the urine?
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protein error of indicators
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What causes the change in color indicating the presence of protein on a urine dipstick?
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albumin binding to the dye which shifts the dye's spectrum os the color changes from yellow to green
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The presence of protein in the urine can be quantified by?
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precipitation methods (sulfosalicylic acid)
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How can highly alkaline urine affect protein measurements?
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false positive
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How can sulfosalicylic acid and penicillin affect protein measurements?
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false positive
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What is the best single indicator of renal abnormalities?
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proteinuria
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Proteinuria is associated with what conditions?
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multiple myeloma, orthostatic proteinuria, strenuous exercise
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What is orthostatic proteinuria?
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a benign condition which results in proteinuria after standing
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Periodic monitoring of microalbuminuria benefits patients with what conditions?
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diabetes, hypertension, peripheral vascular disease
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What substance is in such low quantities that routine reagent strips cannot detect its presence?
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microalbumin
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What is the methodology behind the measurement of glucose on a dipstick?
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glucose oxidase (double) sequential enzyme reaction)
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A positive copper reduction test with a negative dipstick test indicates?
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a sugar (or other reducing substance) other than glucose
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Which is more sensitive: copper reduction test or glucose dipstick?
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dipstick
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What interferes with the measurement of glucose on a dipstick?
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bleach (false positive)
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What is the purpose for using a clinitest tablet?
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to detect the presence of other reducing sugars as well as glucose
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What is the methodology behind the clinitest tablet?
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benedict's copper reduction test (CuSO4 + NaOH + reducing substance = Cu2O)
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In benedict's copper reduction test sugars and other reducing substances reduce what substance into?
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cupric ion to the cuprous state (in the presence of alkali and heat)
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The clinitest tablet is generally used as a screening test for?
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galactosemia (a rare congenital carbohydrate metabolic condition in pediatric patients)
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What is the principle of ketone testing performed with a dipstick?
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sodium nitroprusside + ketone = purple color
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What is the dipstick actually detecting when testing for the presence of ketones?
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diacetic acid
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What confirmation test is used to confirm the presence of ketones in the urine?
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acetest tablets
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What are the end products of fat metabolism?
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acetone, diacetic acid (acetoacetate), beta-hydroxy-butyric acid
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What interferes with the measurement of ketones in the urine?
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highly pigmented urine, levadopa metabolites
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Uncontrolled diabetes mellitus, high protein diets and GI disturbances can cause what types of results when testing for ketones?
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positive
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What is the 2-step enzymatic procedure that detects the presence of blood in the urine?
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peroxide on strip + blood = O2, O2 + color producer = color change
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What substances can result in false positive results when testing for the presence of blood?
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bleach, other oxidizing substances
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What substance can result in false negative results when testing for the presence of blood?
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vitamin C
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What other substances also exhibit peroxidase activity?
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hemoglobin, myoglobin
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Hematuria is associated with what clinical conditions?
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systemic bleeding disorders, renal diseases, cystitis, calculi, strenuous exercise
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Hemoglobinuria is associated with what clinical conditions?
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hemolytic anemias, incompatible transfusions, malaria, strenuous exercise
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Myoglobinuria is associated with what clinical conditions?
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muscle destruction
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What is the principle behind the detection of bilirubin in the urine?
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(diazo reaction) diazonium salt + bilirubin = bluish purple color
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Which is more sensitive in the detection of bilirubin: Ictotest tablet or dipstick?
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ictotest
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What substances can lead to false positives in the detection of bilirubin?
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vitamin C, nitrite
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Bilirubinuria is associated with what conditions?
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bile duct obstruction, liver damage (hepatitis and cirrhosis)
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What is the principle behind dipstick testing of urobilinogen?
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(ehrlich's reaction) para-dimethylaminobenzaldehyde in acid buffer reacts with urobilinogen
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What substances lead to false negatives when testing for urobilinogen?
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nitrite, formalin
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What substances lead to false positives when testing for urobilnogen?
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highly pigmented urine, some medications
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What is the reference range for urobilinogen?
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1 mg/dL or less
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Increased urobilinogen can be indicative for what conditions?
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liver damage, hemolytic disease
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True of False: A negative urobilinogen result cannot be detected on a dipstick.
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true
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A negative urobilinogen result can indicate?
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bile duct obstruction
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During normal bilirubin metabolism hemoglobin is converted into?
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unconjugated bilirubin
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Unconjugated bilirubin once formed goes where and what does it become during bilirubin metabolism?
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liver, conjugated bilirubin
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Once bilirubin becomes conjugated in the liver it then goes where? What does it get turned into then?
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intestine, urobilinogen
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Once urobilinogen is formed, it is sent where?
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1/2 to the feces as urobilin, 1/2 to the liver where it is reabsorbed
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The 1/2 of urobilinogen that is sent the liver is excreted where?
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kidney
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Increased urobilinogen with no bilirubin in the urine indicates what conditions?
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a hemolytic condition
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Increased bilirubin and urobilinogen in the urine indicates?
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liver disease
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Increased bilirubin with decreased urobilinogen indicates what condition?
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bile duct obstruction
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What is the principle behind the detection of nitrite in urine using a dipstick?
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(Griess's reaction) nitrite reacts with amine reagent at acidic pH forming a dizaonium compound, the diazonium compound reacts with 3-hydroxy-1,2,3,4 tetrahydrobenz (h)-quinolin
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What situations can cause a false negative nitrite result?
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lack of dietary nitrite, urine not in bladder long enough, non-nitrate reducing bacteria present, vitamin c
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What is the principle behind the detection of leukocytes in urine using a dipstick?
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leukocyte esterase splits an ester to form a pyrrole compound which reacts with a diazo regent
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A positive pH test correlates with what other tests?
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nitrite, leukocte, microscopic
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A positive protein test correlates with what other tests?
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blood, nitrite, leukocyte, microscopic
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A positive glucose test correlates with what other tests?
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ketone
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A positive bilirubin test correlates with what other tests?
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urobilinogen
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The leukocyte esterase test reacts with what
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