chemical testing

State the clinical significance, reaction, and sources of interference for urine reagent strip testing:

1. pH

   1. used to determine acid-base disorder status

      1. manage disorders that need urine maintained at a certain pH (renal crystals and calculi, UTIs)

   2. reaction: 

      1. double indicator system w methyl red and bromothymol blue

         1. pH 4-6 red orange-yellow

         2. pH 6-9 green - blue

      2. sensitive for pH 5-9

   3. sources of interference

      1. old specimen (pH 9)

      2. run over from adjacent pads

2. protein

   1. clinical significance

      1. proteinuria= increased protein in urine

         1. pre-renal is not caused by kidney disease

            1. caused by acute phase reactants (inflammation and infection), hemoglobin (IV hemolysis), myoglobin (muscle injury), and bence jones proteins (multiple myeloma)

         2. renal

            1. glomerular proteinuria: damage to glomerular membrane reduces selective filtration

               1. amyloid, toxic substances, immune complexes

            2. tubular proteinuria

               1. toxins, heavy metals, viruses, fanconi syndrome

            3. orthostatic proteinuria

               1. occurs in young adults

               2. postural - follows period of time spent in a vertical position

            4. microalbuminuria:

               1. diabetes type I and II

               2. cardiovascular disease

         3. post-renal: protein occurs after passing thru lower urinary tract

            1. bacterial or fungal infections

            2. contamination from menstruation or sperm

            3. prostatic fluid

   2. reaction:

      1. uses tetrabromophenol blue as a color change on the indicator

      2. + is yellow → blue green

      3. sensitivity of 15-30 mg/dl albumin

   3. sources of interference

      1. false +

         1. highly buffered alkaline urine

         2. pigmented specimen

         3. antiseptics

         4. high specific gravity

      2. false -

         1. proteins other than albumin 

         2. microalbuminuria

         3. drugs that mask results

   4. SSA test can provide confirmation of protein on a dipstick

      1. sulfosalicylic acid is added to urine and protein precipitates, the turbidity is then read and graded

3. glucose

   1. clinical significance

      1. used to diagnose and monitor diabetes

      2. if blood glucose becomes elevated, tubular transport if glucose stops and glucose appears in urine

      3. fasting specimens are recommended to evaluate glucose

   2. reaction:

      1. glucose oxidase reagent pad is a double sequential enzymatic rxn

      2. blue → greens/browns to measure

      3. sensitivity of 75-125 mg/dl

   3. sources of interference

      1. false +

         1. oxidizing agents (bleach contamination)

         2. peroxides

      2. false -

         1. incrs ascorbic acid levels

         2. incrs ketone levels

         3. low T

         4. improper preservation

   4. CLINTEST is subject to interference from other sugars and is NOT confirmatory for glucose

4. ketones

   1. clinical significance:

      1. ketones are produced in urine when the body increases fat metabolism

         1. inability to metabolize carbs (diabetes type I)

         2. increased loss of carbs (vomiting)

         3. decreased carb intake (malabsorption or starvation)

      2. urine ketone testing is the most significant in the management of insulin dependent type I diabetes. Increased ketones indicates a deficiency of insulin in the body

         1. increase ketones in the blood may cause electrolyte imbalance, dehydration, acidosis (diabetic coma)

   2. reaction

      1. sodium nitroprusside rxn, tan to purple

      2. sensitivity 5-10 mg/dl acetoacetic acid

   3. sources of interference

      1. false +

         1. phthalein dyes used in determining kidney function

         2. highly pigmented red urine

         3. medications

      2. false  -

         1. improper preservation

5. blood

   1. positive blood urine can indicate

      1. hematuria (intact RBCS)

         1. cloudy or smoky urine

         2. color varies on cells present

         3. often indicative or kidney damage

            1. renal stones

            2. glomerular disease

            3. tumors

            4. taruma

            5. pyelonephritis

            6. toxin or anticoagulant exposure

         4. non-patho include periods and strenuous exercise

      2. hemoglobinuria (lysed RBCs)

         1. clear or red/brown urine

         2. hemolyzed plasma

         3. can result from

            1. lysis of RBCs in urinary tract (hematuria also present)

            2. IV hemolysis

         4. hemosiderin or yellow-brown granules of storage urine can also be found in tubular renal epithelial cells

      3. myoglobinuria

         1. red-brown urine

         2. normal plasma

         3. myoglobin is associated with muscle wasting

            1. rhabdo

            2. trauma

            3. crush syndromes

            4. muscle wasting diseases

            5. alcohol and drug abuse

            6. cholesterol meds

   2. reaction:

      1. uses pseudoperoxidase activity of heme

      2. intact RBCs are lysed on reagent pad and appear as speckled pattern on reagent strip 

      3. + strip reaction needs further differentiation

      4. sensitivity:

         1. 5-20 RBCs/ml

         2. .0015-.0062 mg/dl hemoglobin

   3. sources of interference 

      1. false +

         1. strong oxidizing agents

         2. bacterial peroxidases

         3. period contamination

      2. false -

         1. high specific gravity

         2. high nitrate conc

         3. ascorbic acid >25 mg/dl

         4. not mixing before testing

6. bilirubin

   1. clinical significance:

      1. may indicate liver disease

   2. reaction:

      1. uses a diazo reaction to determine presence

      2. color rxns are the hardest to determine

   3. sources of interference

      1. false +

         1. highly augmented urine

         2. indican presence

      2. false -

         1. light exposure

         2. ascorbic acid >25 mg/dl

         3. high nitrate conc

7. urobilinogen

   1. clinical significance

      1. increased urobilinogen is detected in liver disease and hemolytic disorders

   2. reaction

      1. multistix use erlichs aldehyde rxn on the strip creating a color rxn with varying colors of pink

      2. unable to detect absence, significant in biliary obstruction

      3. sensitivity of 0.2 mg/dl

   3. causes of interference

      1. false +

         1. porphobilinogen

         2. indican

         3. p-aminosalicylic acid

         4. sulfonamides

         5. pigment urine

      2. false -

         1. old specimen

         2. formalin preservation

8. nitrite

   1. clinical significance

      1. provides indication of UTI

      2. monitoring of abx therapy

      3. periodical screening of high-risk

         1. pregnant

         2. diabetic

      4. recurrent UTIs

   2. reaction:

      1. greiss rxn, any pink color indicates +

      2. sensitivity 0.0.6-0.1 mg/dl nitrate ion

   3. sources of interference

      1. false +

         1. improper preservation

         2. highly pigmented urine

      2. false -

         1. non reductase containing bacteria

         2. insufficient contact time

         3. lack or urinary nitrate

         4. large quantity of bacteria converting nitrate to nitrogen

         5. abx

         6. ascorbic acid

         7. high specific gravity

      3. true + should also accompany a + leukocyte esterase test

9. leukocyte esterase

   1. clinical significance:

      1. detects presence of esterase from leukocytes in the urine, indicates UTI

   2. reaction:

      1. diazo salt and pyrrole amino ester rxn

      2. rxn requires  2 min before reading

      3. purples = +

      4. sensitivity: 5-15 WBCs/high power field

   3. sources of error

      1. false +

         1. string oxidizing agents

         2. formalin

         3. highly pigmented urine

            1. AZO!

            2. beets

         4. vaginal contamination

      2. false -

         1. high conc of

            1. glucose

            2. protein

            3. oxalic acid

            4. ascorbic acid

            5. abx

         2. inaccurate timing

         3. lymphocytes

         4. soaps or detergents

         5. high specific gravity

10. specific gravity

    1. clinical significance

       1. hydration status of pt

       2. loss of renal concentrating ability

       3. diabetes insipidus

    2. reaction:

       1. measures ionic solute conc

       2. pH type reading assoc w a specific gravity number

       3. sensitivity: 1.00-1.030

    3. sources of interference:

       1. false +

          1. high protein conc

          2. ketoacids

       2. false -

          1. highly alkaline urine

          2. glucose > 1g/dl

Define the following terms:

1. Proteinuria: protein in urine

2. Isosthenuria: specific gravity of 1.010

3. Hyposthenuria: specific gravity less than 1.010

4. Hypersthenuria: specific gravity greater than 1.010

Compare and contrast causes of proteinuria:

1. prerenal is not caused by kidney disease

   1. caused by acute phase reactants (inflammation and infection), hemoglobin (IV hemolysis), myoglobin (muscle injury), and bence jones proteins (multiple myeloma)

2. renal

   1. glomerular proteinuria: damage to glomerular membrane reduces selective filtration

      1. amyloid, toxic substances, immune complexes

   2. tubular proteinuria

      1. toxins, heavy metals, viruses, fanconi syndrome

   3. orthostatic proteinuria

      1. occurs in young adults

      2. postural - follows period of time spent in a vertical position

   4. microalbuminuria:

      1. diabetes type I and II

      2. cardiovascular disease

3. post-renal: protein occurs after passing thru lower urinary tract

   1. bacterial or fungal infections

   2. contamination from menstruation or sperm

   3. prostatic fluid

Explain the confirmatory or alternative testing principles for:

1. Protein

   1. Sulfosalicyclic Acid (SSA)

2. Glucose

   1. CLINITEST

      1. measures presence of reducing sugars based on copper reduction method

         1. can also detect lactose, fructose, galactose, and pentose

      2. NOT confirmatory

3. Ketones

   1. Acetest

      1. used to determine false +, tablets create a color reaction

4. Bilirubin

   1. Ictocheck

      1. used to confirm, more sensitive and less subject to interference

5. Urobilinogen

   1. Watson Schwartz

      1. used to distinguish urobilinogen from porphobilinogen

      2. observe layering after mixing

         1. red bottom = urobilinogen

         2. red top = porphobilinogen

Compare and contrast hematuria, hemoglobinuria and myoglobinuria.

1. hematuria (intact RBCS)

   1. cloudy or smoky urine

   2. color varies on cells present

   3. often indicative or kidney damage

      1. renal stones

      2. glomerular disease

      3. tumors

      4. taruma

      5. pyelonephritis

      6. toxin or anticoagulant exposure

   4. non-patho include periods and strenuous exercise

2. hemoglobinuria (lysed RBCs)

   1. clear or red/brown urine

   2. hemolyzed plasma

   3. can result from

      1. lysis of RBCs in urinary tract (hematuria also present)

      2. IV hemolysis

   4. hemosiderin or yellow-brown granules of storage urine can also be found in tubular renal epithelial cells

3. myoglobinuria

   1. red-brown urine

   2. normal plasma

   3. myoglobin is associated with muscle wasting

      1. rhabdo

      2. trauma

      3. crush syndromes

      4. muscle wasting diseases

      5. alcohol and drug abuse

      6. cholesterol meds