Laboratory Tests

URINALYSIS

Generally divided into two parts:

General: Includes macroscopic evaluation, specific gravity, and a dipstick segment
Microscopic evaluation: Quantitative assessment of cellular component

Specific Gravity

Normal value: 1.003 to 1.035

Measures the kidney’s ability to concentrate urine; the higher the value, the more concentrated the urine

Red	Orange	Blue/Green or Black
Hemoglobinuria	Restricted fluid intake	Lysol poisoning
Hematuria	Concentrated urine	Melanin
Myoglobinuria	Urobilin	Bilirubin
Porphyrins	Fever	Methemoglobin
Menstrual	Porphyrin	Pseudomonas toxemia
Contamination

Specific Gravity
Increased in	Decreased in
Diabetes mellitus	Diabetes insipidus
Volume depletion
Dehydration
Fever
Vomiting
Diarrhea

Color

Normal: Yellow, straw-colored, amber

In addition to the following, many medications and foods can alter urine color.

Appearance

Normal: Clear

Cloudy urine indicates a UTI.

Smell

Fresh urine has an aromatic ammonia smell.

Sweet smell: Smell of acetone on diabetic ketosis

Putrid smell: Presence of bacteria

Maple syrup smell: Due to a genetic disorder called maple sugar urine disease. An enzymatic defect (branched-chain keto acid decarboxylase) renders the children unable to break down branched-chain amino acids and they accumulate in the urine.

Normal value: 4.6 to 8.0

Acidic	Basic
High-protein (meat) diet	UTI
Starvation	Vomiting
Diabetes	Old urine specimen
COPD

Blood

Normal value: 0 to trace amounts

A positive test has three possible implications because the reagent is sensitive to RBCs, free Hb, and myoglobin.

Hematuria (RBCS)	Hemoglobinuria (FREE Hb)	Myoglobinuria (A Muscle Protein)
UTI	Burns	Traumatic muscle injury
Lupus	Crush injury	Electric shock
Polyarteritis nodosa	Transfusion reaction	Muscular dystrophies
Malignant hypertension	Febrile intoxication
Subacute bacterial	Malaria
Endocarditis	Glomerulonephritis
Trauma
Heavy smoker

Glucose

Normal value: 0 to trace amounts

GLUCOSURIA

Diabetes mellitus

Brain injuries

Severe stress

Drugs (ASA, epinephrine)

Ketones (Acetone)

Normal value: 0 to trace amounts

Children are particularly prone to develop ketonuria. Ketone bodies appear in the urine before there is any significant increase in the blood.

KETONURIA

Uncontrolled diabetes

Starvation

Fever

Prolonged vomiting

Diarrhea

Leukocyte Esterase

Normal value: 0 to trace amounts

Positive results indicate pyuria (pus in the urine).

INCREASED IN

UTIs

Nitrite

Normal value: 0 to trace amounts

Bacteria convert nitrates to nitrites. False negatives are not uncommon as not all bacteria convert nitrates to nitrites.

NITRITURIA (greater than trace amounts in urine)

UTIs

Protein

Normal value: 0 to trace amounts

Generally refers to the albumin levels since albumin represents the bulk of blood protein. The term albuminemia is often used interchangeably with proteinuria. Bence Jones protein is a specific globulin protein, which, when found in urine, is suggestive of multiple myeloma.

PROTEINURIA (greater than trace amounts in urine)

Usually indicates some form of renal disease

Nephritis/glomerulonephritis

Nephrosis

Polycystic kidney

CA of the kidney

Pyelonephritis

Other nonrenal causes include the following:

Fever

Trauma

Severe anemia and leukemia

Toxemia, preeclampsia of pregnancy

Intestinal obstruction

Abdominal tumors

Convulsive disorders

Hyperthyroidism

Liver disease

Acute infection

Transient proteinuria may be associated with the following:

Severe exercise

Severe emotional stress

Cold baths

Urobilinogen

Normal values: 0 to trace amounts

Urobilinogen is metabolized in the liver and excreted in bile; if the liver is unable to metabolize urobilinogen, either due to problems with the liver or excessive amounts of urobilinogen, it ends up in the urine.

INCREASED IN

Hepatitis (infectious or toxic)

Hemolytic anemia

Pernicious anemia

Malaria

RBCs

Less than three cells per high-power field (hpf)

INCREASED IN

Trauma

Cystitis

UTI

Tumors

Stones

Prostatitis

Lupus

Polyarteritis nodosa

Malignant hypertension

Subacute bacterial endocarditis

Glomerulonephritis

Pyelonephritis

Heavy smoker

WBCs

Less than five cells per high-power field (hpf)

INCREASED IN

UTIs

Pyelonephritis

Most renal disorders

Epithelial Cells

Less than two cells per high-power field (hpf)

INCREASED IN

Acute tubular damage

Crystals

The presence of crystals in urine is a normal finding. The type and number vary according to the pH.

Casts

Casts are a general indicator of kidney disorders. Named because their shape represents the cylindrical shape of the kidney’s tubular lumen. Different types of casts are so-named for the cells or cellular components they contain.

HYALINE CASTS

Empty casts containing no cellular components. They are normal unless very numerous, which could be due to low urine flow.

RBC CASTS

Indicate glomerulonephritis

WBC CASTS

Indicate pyelonephritis

EPITHELIAL CASTS

Indicate tubular damage

GRANULAR CASTS

Cellular casts (e.g., RBC casts, WBC casts) break down to granular casts. They are nonspecific and associated with any form of nephritis.

WAXY CASTS

Waxy casts are the end stage of granular casts.

FATTY CASTS

Occur in any form of nephritis, esp. nephrotic syndrome and Fabry dz

CBC WITH DIFFERENTIAL

WBC

Normal value: 5,000 to 10,000 per µL

Measures the total number of circulating leukocytes

Leukopenia	Leukocytosis
(<4,000/µL)	(>10,000/µL)
Overwhelming infection	Bacterial infection
Viral infection	Inflammatory process
Hypersplenism	Tissue necrosis (MI, burns)
Bone marrow depression	Physical stress

Differential

A “differential” determines the relative amounts of each of the five types of WBCs, which is more diagnostically valuable than just the total number of WBCs alone.

Types	Normal Values	Significances of Increase
Neutrophils (total)	50%-70% (2,500-7,000/µL)	Bacterial infections
Segments	50%-65% (2,500-6,500/µL)	Right shift^*—liver dz, some types of anemia
Bands	0%-5% (0-500/µL)	Left shift^*—acute bacterial infection
Eosinophils	1%-3% (100-300/µL)	Allergic and parasitic diseases
Basophils	0.4%-1.0% (40-100/µL)	Source of histamines—inflammation/allergies
Monocytes	4%-6% (200-600/µL)	Viral infection, TB, parasitic diseases, subacute bacterial endocarditis, monocytic leukemia, collagen dz
Lymphocytes	25%-35% (1,700-3,500/µL)	Viral infection, lymphocytic leukemia
^*Normally, most circulating neutrophils are in their mature form which the laboratory identifies by its segmented nucleus (segmented neutrophils). In contrast, the nucleus of less mature neutrophils is not yet segmented but still seen as a band (band neutrophils).
When lab reports were written by hand, the bands were written first on the left side of the page and the segments to the right, hence the terms left shift and right shift.

RBC

Normal value: Average—4,600,000 per µL (higher in males)

The average life span of a RBC is 120 days.

Decreased RBCs are found in anemia (for more specific diagnosis, evaluate Hct, Hb, and indices). Increase in RBCs is termed polycythemia and is associated with many factors that cause overproduction of RBCs or a decrease in plasma. Polycythemia is associated with many factors, including dehydration, acute poisoning, severe diarrhea, and pulmonary fibrosis.

Hematocrit (Hct)

Average value is 45% (higher in males)

Hematocrit is the percentage volume of RBCs in a sample of anticoagulated whole blood. Hematocrit decreases in anemia and blood loss. Useful when evaluating bleeding or blood loss. The body reacts to blood loss by dumping more fluids into the vascular system to maintain BP. This excess fluid does not contain RBCs, and hematocrit decreases.

Hemoglobin (Hgb, Hg, Hb)

Normal value: (Average) male 16, female 14

Decreased in anemia; increased in polycythemia

Indices (RBC Indices)

Provide information about the size and hemoglobin content of red blood cells. Indices are a useful aid in differentiating anemias.

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