Aubf prelim 5

pH

Controlled by dietary regulation

4.5-8.0

Normal range of pH

First morning specimen

This is usually acidic (5.0-8.0)

pH above 8.0

This is associated with an improperly preserved specimen

Acidic urine

High protein diet, cranberries, emphysema

Cranberries

This is an alternativefor UTI or minor bladder infection

- inhibits colonization of pathogen

Alkaline pH

Vegetarian diet, prolonged standing, hyperventilation

Pathologic conditions of acidic urine

Diabetes mellitus, diarrhea, starvation, dehydration, respiratory/metabolic acidosis, E. Coli infections

Pathologic condition of alkaline urine

UTI with urea splitting bacteria, renal tubular acidosis, vomiting, respiratory/metabolic alkalosis

Acid base balance disorders

One of the Clinical importance of pH, it helps in evaluating?

renal calculi (stones)

One of the Clinical importance of pH, it aids in management of?

Uric acid, cystine, calcium oxalate stones

Acidic urine favors what kind of renal stones?

calcium phosphate, calcium carbonate, magnesium ammonium phosphate (struvite) stones

Alkaline urine favors what kind of renal stones?

Double indicator system

Principle of pH

Reaction of pH

Direct colorimetric pH measurement

- has no chemical conversion

- each indicator changes color within a specific pH range

Methyl red (pH 4-6)

red in acid, yellow in base

Bromthymol Blue (pH 6-9)

Yellow to blue

orange → yellow → green → deep blue

Color change from pH 5-9

No known interference

Sources of Errors in pH

Correlations with other urine tests:

nitrite

leukocyte esterase

protein

microscopy

alkaline urine w/_________ indicates UTI from urea-splitting bacteria

nitrite (correlations w/pH)

Alkaline pH + ________________ support bacterial infection or inflammation.

Leukocyte Esterase (correlations w/pH)

Alkaline urine may give a false-positive __________ result.

Protein (correlations w/pH)

may lyse RBCs or WBCs

Microscopy (correlations w/pH)

protein

early marker of renal damage

proteinuria

The most important indicator of renal disease.

- clinical significance of protein

types of proteinuria

- pre-renal

- renal

- post-renal

pre-renal

Proteinuria caused by conditions before the kidney

- plasma related

- missed in the chemical examination

causes of pre-renal proteinuria

- hemolysis (hemoglobin)

- muscle injury (myoglobin)

- acute phase reactants associated with infection and inflammation

Bence Jones protein

Excretion by persons with multiple myeloma

- proliferative disorders of plasma cells

renal

associated with true renal disease

- glomerular protienuria

- microalbuminuria

- orthostatic (postural) proteinuria

glomerular protienuria

Damage to the glomerular membrane due to loss of selective filtration

- Increased glomerular pressure

- Serum proteins, RBCs, WBCs leak into urine

4g/day

How many grams of serum proteins, RBCs, and WBCs leak into urine per day?

amyloid, toxins, and immune complexes (systemic lupus erythematosus) (poststreptococcal glomerulonephritis)

major causes of glomerular proteinuria

pregnancy

proteinuria + hypertension = pre-clampsia

Microalbuminuria

Small increase in albumin not detected by routine strips.

- common in type 1&2 diabetes

- diabetic nephropathy

- increased risk of cardiovascular disease.

Orthostatic (Postural) Proteinuria

occurs in following periods spent in a vertical posture and disappears when a horizontal position is assumed

- Increased pressure on renal vein in vertical posture.

- empty bladder before sleep

- collect first morning spec

- Collect 2nd sample after standing for 8 hrs

tetsing of orthostatic proteinuria

1st spec = neg

2nd spec = pos

Positive for orthostatic proteinuria

tubular proteinuria

Defective tubular reabsorption of normally filtered proteins

- Albumin + other low-molecular weight proteins

- Exposure to toxic substances/heavy metals

- severe viral infections

- Fanconi syndrome

causes of tubular proteinuria

post renal

Protein added after urine formation

- Bacterial or fungal infections

- Blood contamination

- w/prostatic fluid

- w/ large amt. of spermatozoa

interstitial fluid

Bacterial or fungal infections produce protein-rich exudates which are from the?

Protein error of indicators

principle of protein

- more sensitive to albumin (more amino groups) that other proteins

protein (albumin) accepts H⁺ ions

Mechanism of protein error of indicators

yellow(negative) -> blue green (increase prot. conc.)

reaction of protein error of indicators

15-30 mg/dL

sensitivity of protein error of indicator to albumin

False positives to protein error of indicators

- highly alkaline urine

- prolonged strip immersion

- contamination with quaternary ammonium compounds

- detergents

- antiseptics

false negatives to protein error of indicators

proteins other than albumin

Sulfosalicylic acid (SSA)

Confirmatory test for protein

- detects all types of prot

- used when questionable results/clinical suspicion is high

albumin, globulins, Bence Jones protein

Sulfosalicylic acid (SSA) detects

Correlation with other urine tests

blood

leukocyte esterase

nitrite

pH

spec. gravity

microscopy

glomerular disease or hemolysis/rhabdomyolysis

blood (correlation w/ protein)

urinary tract infection with inflammation

Leukocyte Esterase & Nitrite (correlation w/ protein)

false-positive protein results

pH (correlation w/ protein)

High SG = false-positive, Low SG = renal damage

specific gravity (correlation w/ protein)

w/ casts = renal origin, w/ crystals = stone fomation

microscopy (correlation w/ protein)

Glucose

Most frequently performed urine chemical test

- ususally not detectable

less than 70mg/dl

Normal urine glucose is mostly

diabetes mellitus

glucose testing in chem test is usually for detection & monitoring of?

- Most common cause of glycosuria = hyperglycemia exceeding rrenal threshold

160-180mg/dl

Renal threshold for glucose

fasting specimen

recommended for screening glucose

2hr postprandial

specimen useful for DM monitoring

First morning specimen

The specimen may not be fasting for testing glucose (residual glucose overnight)

glycosuria

occurs when blood glucose is above the renal threshold

Gestational Diabetes

Hyperglycemia that occurs during and disappears after pregnancy

6th month

Gestational Diabetes onset is on the ___ month of pregnancy

placental hormones

This causes insulin resistance, which causes hyperglycemia

macrosomia

fetus develops hyperinsulinemia due to the high levels of glucose, leading to?

- obesity/type 2 DM

renal glycosuria

Disorders with increased anti-insulin hormones:

PACHPT

Pancreatitis, Acromegaly, Cushing Syndrome, Hyperthyroidism, Pheochromocytoma, Thyrotoxicosis

PACHPT

glucagon, epinephrine, cortisol, thyroxine, and growth hormone

These work in opposition to insulin

double sequential enzyme reaction

principle of glucose

glucose oxidase testing method

impregnating testing area with a mixture of glucose oxidase, peroxidase, chromogen, and buffer

Glucose + O₂ → Gluconic acid + H₂O₂

Peroxidase + chromogen → green to brown

glucose oxidase testing method

Chromogens

Potassium iodide

Tetramethylbenzidine

Potassium iodide

multistix: green to brown

Tetramethylbenzidine

chemstrip: yellow to green

75-125 mg/dl

glucose sensitivity of double sequetial enzyme method

False positives in glucose

strong oxidizing agents (bleach)

False negatives in glucose

- ascorbic acid

- strong reducing substances

- improperly stored urine(bacterial metabolism)

clinitest (copper reduction test)

uses benedict's reaction

Blue → Green → Yellow → Orange/Red

benedict's reaction

reducing sugars reduce cupric sulfate (Cu²⁺) to cuprous oxide (Cu⁺) in the presence of alkali and heat.

effervescent reaction

produces heat + CO₂, preventing interference from room air.

poor glycemic control or diabetic ketoacidosis (DKA).

ketone (correlation w/ glucose)

High SG = osmotic diuresis

specific gravity (correlation w/ glucose)

diabetic nephropathy or renal damage

protein (correlation w/ glucose)

ketoacidosis

pH (correlation w/ glucose)

yeast cells = glycosuria promoting infection

microscopy (correlation w/ glucose)

ketones

Intermediate products of fat metabolism

- acetone

- acetoacetic acid

- B-hydroxybutyrate

acetone

has 2% of ketones

- weakly detected

Acetoacetic acid

has 20% of ketones

- key compund in detection of ketones in urine

B-hydroxybutyrate

has 70% of ketones

- not detected

carbon dioxide and water

fat is fully metabolized into whta?

type 1 diabetes mellitus

this is where insulin is absent or insufficient, so glucose cannot be used for energy.

- The body switches to fat metabolism, producing large amounts of ketones.

diabetic ketoacidosis

Increase accumulation of ketones in the blood

- Electrolyte imbalance

- Dehydration

- Metabolic acidosis

- Diabetic coma

diabetic ketoacidosis is because of?

carbohydrate deficiencies

this is due to poor intake or absorption of carbohydrates

- Prolonged vomiting or diarrhea

- fat burning

- Frequent strenuous exercise

Prolonged vomiting or diarrhea

accelerates the loss of carbohydrate stores.

fat burning

used as compensation for patient who avoids carbohydrates (weight loss/ eating disorder)