Cheical Examination of Urine：尿液化学检验

1、chemical examination of urinericki otten mt(ascp)sc2objectives: review the objectives on page 1 and 2 of the lecture handout objectives marked with * will not be tested over during student lab rotation3historical perspective: urinalysis physical examination of urine odor taste color cl

2、arity4historical perspective chemical examination of urine limited reactions required large volumes of urine large volumes of reagent performed in test tubes time consuming and cumbersome clinical usefulness was not realized not routinely ordered5historical perspective microscopic examination of uri

3、ne not until invention of the microscope then clinical usefulness realized6reagent strip testing technology and necessity chemical reactions miniaturized required less urine test results within minutes easy to perform increased test utilizationbrunzel, 2nd ed, page 1247reagent strip testing ideal qu

4、alitative screening tool sensitive: low concentration of substances negative result = normal specific: reacts with only one substance false negative and false positive cost effective: relatively inexpensive tool that provides information about the health statusof the patient8reagent strip testing ch

5、emically impregnated absorbent pads attached to an inert plastic strip each pad is a specific chemical reaction thattakes place upon contact with urine chemical reaction causes the color of the pad tochange color compared to a color chart for interpretation9reagent strip testing qualitative or semi-

6、quantitative results concentration units (mg/dl) negative, small, moderate large negative, 1+, 2+, 3+, 4+ timing of chemical reactions is critical shortest time requirement on one end of strip: 30 sec longest time requirement on the other: 2 min10reagent strip testing principle of chemical reactions

7、 false negative reactions false positive reactions color interferences alternative testing: used to confirm results that you may think are invalid due to interfering substance color interference (called color masking)11care and storage (pg 4)confirmatory testing (pg 6)reading assignment:textbook, ch

8、apter 7page 124-13012confirmatory testing alternative testing establishes the correctness or accuracy of another procedure often used when urine is highly pigmented bilirubin reagent strip ictotest13confirmatory testing characteristics: differ in sensitivity ictotest vs bilirubin reagent strip diffe

9、r in specificity ssa vs protein reagent strip clinitest vs glucose reagent strip differ in methodology/reactionideallywant all 314differ in specificity clinitest reacts with all reducingsubstances glucose reagent strip reacts with only one reducing substance: glucose1510 reagent strip tests specific

10、 gravity ph protein glucose ketones blood bilirubin urobilinogen nitrite leukocyte esterase purpose of the test what is normal what is abnormal reaction causes of invalid results16specific gravity: purpose evaluates the concentrating and dilutingability of the kidney density is related to the amount

11、 of substances (solutes) in solution increased density increased solute in solution hypertonic urine concentrated urine decreased density decreased solute in solution hypotonic urine dilute urine17specific gravity: normal normal: 1.002 1.035 majority of urines: 1.010 1.025 physiologically impossible

12、:1.0001.040 dependent upon hydration status18specific gravity: terms isosthenuria fixed at 1.010 renal tubules lost absorption and secreting capability hypersthenuria increased specific gravity concentrated urine hyposthenuria decreased specific gravity dilute urinesensitivity issues:pregnancy testi

13、ngurinary tract infection19specific gravity: methods methods of measurement reagent strip test: indicates ionic solutes refractometer: indicates amount of total solutes two functions of the kidney maintain water balance maintain electrolyte homeostasisperformed by renal tubules through concentrating

14、 and diluting; reabsorbing and secreting water and electrolytes (ionic)20specific gravity: reaction based on a change in the pka of a polyelectrolyte on the reagent pad increased ions in solution causes the polyelectrolyte on the pad to produce free h+ free h+ cause a change in ph on the reagent pad

15、 change in ph: bromthymol blue indicator21specific gravity: reaction22specific gravity sensitivity: 1.000 specificity: detects only ionic substances radiographic dye mannitol glucosedoes not interfere23ph: purpose kidneys regulate bodys acid-base balance by selective handling of h+ and hco3- urine p

16、h reflects acid-base status of body treatment protocol may require urine ph be maintained at a specific ph(aids in identification of crystals (microscope)24ph: normal normal: ranges from 4.5 8.0 first morning void: acidic physiologically impossible:8.01. urine not handled properly2. old urine3. trea

17、tment induced25ph: interpretation made in conjunction with acid-base status renal function presence of infection in urinary tract diet: high protein, low protein medications age of urine sample26ph: abnormal acid respiratory acidosis high protein diet starvation uti alkaline respiratory alkalosis ve

18、getarian diet renal tubular acidosis uti27ph: reaction double indicator system methyl red bromthymol blue amount of free h+ influences acidity of urine and cause ph indicator to change colorneeded to measure the wide ph range: acid to alkaline28ph: invalid test results due to: improper handling of u

19、rine sample contamination of urine vessel prior to collection run-over phenomenon 29protein: purpose normal kidneys secrete little protein15 mg/dl (or 8.0) false negative: dilute urine presence of other proteins (tamm-horsfall, globulins, myoglobin, free light chains, hemoglobin)35protein: ssa (exto

20、ns test) sulfosalicylic acid (ssa) precipitation test acid will precipitate proteins out of solution causing the solution to become cloudy amount of cloudiness is related to the amount of protein present36protein: ssa (extons test) amount of cloudiness is evaluated, thus must use centrifuged urine s

21、ensitivity: 5-10 mg/dl specificity: detects all protein37protein: ssa (extons test) false positive results: radiographic dyes turbid urine uncentrifuged urine false negative results: highly alkaline urine dilute urine38protein: foam test shake aliquot of urine and observe color of resulting foam whi

22、te foam: protein present39protein: micro-albumin test measures very low concentration of albumin (better sensitivity than reagent strip test for albumin) management of diabetic patient methods vary: reagent strip test,immunochemical reaction40glucose: purpose healthy normal urine does not contain gl

23、ucose normally, glucose is filtered by the glomerulus and is reabsorbed back into the bloodstream through active transport mechanism glucose in urine is pathologic41glucose: purpose glucosuriaglycosuria caused by renal and non-renal disease pre-renal glycosuria: plasma glucose level exceeds renal th

24、reshold (diabetes mellitus) renal glycosuria: plasma glucose level below renal threshold, but tubules cannot reabsorb glucose back into bloodstreamterms used interchangeably 42reducing substances: purpose reducing substances: glucose other sugars: galactosemia (inherited metabolic disorder)43glucose

25、, reducing substances normal: negative abnormal: diabetes mellitus: glucose impaired renal tubular reabsorption: glucose inborn error of metabolism: galactosemia44methods reagent strip: detects only glucose copper reduction: detects reducing substances45glucose: reagent strip detects only glucose do

26、uble sequential enzyme reaction46glucose: reagent strip sensitivity: 30 mg/dl specificity: reacts only with glucose false positive: strong oxidizing agents (bleach) peroxides false negative: ascorbic acid (reducing agent) improperly stored urine: glycolysis47clinitest reaction copper reduction test:

27、 reducing substances are able to reduce copper sulfate to cuprous oxide pass-through phenomenon all children 2 years: metabolic disorder(galactosemia)48clinitest reaction sensitivity: 250 mg/dl specificity: reacts with all reducing substances reducing sugars: glucose, galactose, fructose, lactose, m

28、altose (not sucrose) false positive: any reducing substance(ascorbic acid) false negative: radiographic dye49ketones: purpose ketones are intermediary products of fat metabolism50ketones three ketone bodies acetone2% acetoacetic acid20% beta-hydroxybutyric acid78% characteristic fruity breath aceton

29、e51ketones: normal normal: negative abnormal: inability to utilize carbohydrates excessive loss of carbohydrates inadequate intake of carbohydrates52ketones: methods reagent strip acetest: tablet test53ketones: method glycine: also measures acetone reagent strip: check package insert acetest tablets

30、: contain glycine54ketones reagent strip sensitivity: 5-10 mg/dl specificity: acetoacetic acid and/or acetone false positive: highly pigmented urine false negative: improper specimen handling acetest specificity: acetoacetic acid and acetone false positive: highly pigmented urien false negative: imp

31、roper specimen handling55blood: purpose blood in urine indicates pathology two forms found in urine intact rbc hemolyzed rbc56blood: terms hematuria hemoglobinuria myoglobinuriaall will give a positive blood reaction57blood: reagent strip test can detect hemolyzed rbc heme moiety imparts peroxidase

32、activity and catalyzes the reaction58blood sensitivity specificity intact rbc hemolyzed rbc (hemoglobin) myoglobin false positives: myoglobin, oxidizing agents false negatives: ascorbic acid59blood: correlate reagent strip results microscopic findings color and clarity60bilirubin and urobilinogen bi

33、lirubin in urine is always pathologic: liver disease urobilinogen in urine: normal to have a small amount: 0.2 1.0 mg/dl61three mechanisms pre-hepatic: liver is healthy hepatic: liver disease post-hepatic: liver is healthy, obstruction indicated62bilirubin: methods reagent strip ictotest: tablet tes

34、t foam test63bilirubin: methods reagent strip ictotest: tablet test same reaction same specificity: conjugated bilirubin false positive: urine color false negative: low concentration, ascorbic acid, improper specimen handling64bilirubin: methods reagent strip ictotest: tablet test sensitivity differ

35、sreagent strip: 0.5 mg/dlictotest: 0.05 0.1 mg/dl 65bilirubin: methods possible to have a negative reagent strip test and positive ictotest difference in sensitivity levels always perform ictotest when urine bilirubin test specifically ordered urine appearance is amber: even if bilirubinreagent stri

36、p test is negative positive reagent strip test66bilirubin: foam test shake urine and observe resulting foam yellow foam = bilirubin67urobilinogen: methods reagent strip test two reactions dependent upon manufacturer para-dimethylaminobenzaldehyde diazonium salt cannot determine absence of ubg watson

37、-schwartz assay68urobilinogen: methods para-dimethylaminobenzaldehyde sensitivity: 0.2 mg/dl specificity: false positive: any ehrlich reactive compound; color masking; urine at body temp false negative: improper specimen handling diazonium salt sensitivity: 0.4 mg/dl specificity: reacts only with ub

38、g false positive: color masking false negative: improper specimen handling69urobilinogen: watson schwartz classic method used to differentiateurobilinogen from porphobilinogen using adifferential extraction method para-dimethylaminobenzaldehyde70nitrite: purpose bacteria that contain a specific enzyme can reduce dietary nitrates to nitrites rapid screening test for uti71nitri