Test ID: UMIC
Urinalysis, Microscopic, Osmolality, and pH

Screening for urinary tract diseases and some nonrenal diseases

When this test is ordered, either automated or manual microscopic examination will always be performed at no additional charge.

UOSMU: Freezing Point Depression

PHU_: ph meter

UBIL: ICOTEST

HGBQL: Dipstick

UREDU: Clinitest

Container/Tube: Plastic, 60-mL urine bottle

Specimen Volume: 20 mL

Collection Instructions: Collect a random urine specimen.

The kidney plays a key role in the excretion of by-products of cellular metabolism and regulation of water, acid-base, and electrolyte balance. Urine is produced by filtration of plasma in the renal glomeruli followed by tubular secretion and/or reabsorption of water and other compounds.

Abnormalities detected by urinalysis may reflect either urinary tract diseases (eg, infection, glomerulonephritis, loss of concentrating capacity) or extrarenal disease processes (eg, glucosuria in diabetes, proteinuria in monoclonal gammopathies, bilirubinuria in liver disease).

Descriptive report

Microscopy:

Red blood cells (RBCs), white blood cells (WBCs), renal tubular epithelial (RTE) cells, casts, squamous cells, parasites, fat, bacteria, and pathologic crystals are reported. RBCs are almost always indicative of glomerulonephritis. WBC casts are typically an indication of acute interstitial nephritis or pyelonephritis, but can also be seen in glomerulonephritides because there is often a component of accompanying interstitial nephritis. Fatty casts and free fat are often seen in patients with nephrotic syndrome or other glomerular diseases associated with significant proteinuria. Granular casts are observed in a number of disorders and are thought to be formed from partially degraded cellular casts, or are protein-derived casts. Hyaline casts are not thought to be indicative of any disease process, but increased numbers may be seen in concentrated urine specimens. Waxy casts and broad casts are most often observed in advanced renal failure. Increased numbers of RTE cells are indicators of renal tubular injury. Increased numbers of RTE cells may be caused by drugs with renal tubular toxicity (eg, cyclosporine A, aminoglycosides, cisplatin, radiocontrast media, acetaminophen overdose), interstitial nephritis, hypotension (surgical, sepsis, obstetric complications), and heme pigments from hemoglobinuria or myoglobinuria from rhabdomyolysis (eg, alcoholism, heat stroke, seizures, sickle cell trait). Newborns often shed RTE cells in their urine.

Based on careful review of all available published outcome studies with results of detailed hematuria workups within actual patient populations, a panel from the American Urological Association recommends that patients with >3 red cells per high-power field in 2 out of 3 properly collected urine specimens should be considered to have microhematuria, and hence evaluated for possible pathologic causes. However, the panel also noted that there is no absolute lower limit for hematuria, and risk factors for significant disease should be taken into consideration before deciding to defer an evaluation in patients with only 1 or 2 red blood cells per high power field. High-risk patients, especially those with a history of smoking or chemical exposure, should still be considered for a full urologic evaluation even after 1 properly performed urinalysis documented the presence of at least 3 red blood cells per high-power field. In certain patients, even 1 or 2 RBCs per high-powered field might merit evaluation. The presence of squamous cells suggests that the sample may not have been an optimal clean-catch specimen and could be contaminated with skin flora.

Osmolality:

Osmolality is an index of the solute concentration of osmotically active particles, principally sodium, chloride, potassium, and urea. Glucose can contribute significantly to the osmolality when present in substantial amounts. The ability of the kidney to maintain both tonicity and water balance of the extracellular fluid can be evaluated by measuring the osmolality of the urine. More information concerning the state of renal water handling or abnormalities of urine dilution or concentration can be obtained if urinary osmolality is compared to serum osmolality. Normally, the ratio of urine osmolality to serum osmolality is 1.0:3.0, reflecting a wide range of urine osmolality. The reference ranges are as follows 0 to 12 months range is 50 to 750 mOsm/kg. >12 months of age range is150 to 1150 mOsm/kg. Please note above the age of 20 years there is an age dependent decline in the upper reference range of approximately 5 mOsm/kg/yr.

pH:

Urine pH is affected by diet, medications, systemic acid-base disturbances, and renal tubular function. pH may affect urinary stone formation. For example, urine pH <6.0 may help reduce the tendency for calcium phosphate stones and pH >6.0 may reduce the tendency for uric acid stone formation.

Ketones:

Produced during metabolism of fat. Increased ketones may occur during physiological stress conditions such as fasting, pregnancy, strenuous exercise, and frequent vomiting. Ketones may appear in the urine in large amounts, before serum ketone is elevated, under the following conditions:

- diabetic individuals who are unable to efficiently utilize glucose due to a lack of insulin

- starvation

- individuals with other abnormalities of carbohydrate or lipid metabolism

Bilirubin:

Bilirubinuria is an indicator of liver disease and biliary tract obstruction.

Hemoglobin:

Hemoglobinuria is an indicator of intravascular hemolysis. The test is equally sensitive to myoglobin as to hemoglobin (Hgb). The presence of Hgb, in the absence of RBCs, is consistent with intravascular hemolysis. RBCs may be missed if lysis occurred prior to analysis; the absence of RBCs should be confirmed by examining a fresh specimen. The presence of myoglobin may be confirmed by MYOU/9274 Myoglobin, Urine.

Reducing substances:

Urine can contain a variety of reducing substances (sugars [glucose, galactose, sucrose, fructose, lactose, maltose], ascorbic acid, drugs, etc), compounds so termed because of their ability to reduce cupric ions. The primary reducing substances of medical significance are the sugars, glucose (diabetes) and galactose (galactosemia). Other sugars may be found but are not of clinical significance. Because glucose also is detected by glucose-specific dipstick reagents, the test for reducing substances is performed to detect galactose.

Hemoglobin:

Elevated specific gravity, elevated protein, and large amounts of ascorbic acid may cause false-negative results. Oxidizing substances such as hypochlorite and chlorine may cause false-positive results. The test is equally sensitive to hemoglobin and to myoglobin. The presence of Hgb, in the absence of RBCs, is consistent with intravascular hemolysis. RBCs may be missed if lysis occurred prior to analysis; the absence of RBCs should be confirmed by examining a fresh specimen. The presence of myoglobin may be confirmed by MYOU/9274 Myoglobin, Urine.

Reducing substances:

This test reacts with sufficient quantities of any reducing substance in the urine; it is not specific for glucose. Urine specimens with low specific gravity that contain glucose may give slightly elevated results. Metabolites of some sulfa drugs and methapyrilene compounds may interfere with the sensitivity of the test. X-ray contrast media in urine produces reduced and false-negative glucose results.

Grossfeld GD, Litwin MS, Wolf JS, et al: Evaluation of asymptomatic microscopic hematuria in adults: the American Urological Association best practice policy-part I: definition, detection, prevalence, and etiology. Urology 2001;57:599-603

Bilirubin:

Ictotest tablet for Urinalysis (Package insert: Bayer Corporation, Diagnostics Division. Elkhart IN 46515)

Osmolality:

Freezing point depression

pH:

pH meter

Hemoglobin:

AUTION Sticks 9EB for urine chemistry (Package insert: ARKRAY, Inc Japan, distributed by Iris Diagnostics Chatsworth,CA 91311-5874)

Microscopic examination:

Performed on urine sediments by conventional microscopy or by automation using the IRIS iQ200. Determination of which method to use is made by visual inspection. If the urine is a clear, normal color and the amount is adequate (at least 30 mL), the urine is analyzed on the IRIS iQ200. All remaining urines have a manual microscopic examination done on the sediment after centrifuging for 5 minutes at 1400 RPM.

Monday through Sunday; Continuously

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