Microalbuminuria can only be detected by specific immunochemical assays for urinary albumin using antibodies to human albumin. The existing biochemical
1. 1.010 to 1.014—1:1 dilution.
2. 1.015 to 1.021—1:2: : urine : water.
3. 1.022 or more—1:3: : urine : water.
4. If the qualitative test reading is +++, dilute as 1:4: urine:
Bence-Jones (BJ) Protein Tests
Seen in multiple myeloma classically.
1. Heat and Sulfosalicylic Acid
As for albumin, the precipitate formed will contain
both BJ proteins and albumin. Mix the specimen of
urine with the precipitate and divide equally in two test
tubes. Place both in a water bath and heat to boiling.
Remove one from the bath, cool to below 40oC and
compare the turbidity in the two tubes in good light
against a dark background. Cool the other hot tube
and heat the cold one and compare again. If the cold
tube both the times shows persistently a more densely
turbid flocculum of protein, BJ protein is most likely
present. If albumin is present also, add 10% acetic acid
to a fresh urine sample (pH to be less than 6.0) and
bring to boil, keep shaking and break the floc the BJ
protein goes into solution. Filter off albumin while it is
still hot, BJ proteins will come in the filtrate. Repeat the
sulfosalicylic acid test as described above.
Add 1 mL of TSA reagent to 2 mL of urine, let the reagent
flow slowly by the side of the test tube. Mix. A precipitate
appearing within 5 minutes indicates presence of BJ
protein. A negative test excludes.
Electrophoresis of concentrated urine for proteins would
show the dense gammaglobulin band.
Bence-Jones protein is often seen in multiple myeloma and
rarely in chronic leukemia, osteomalacia, osteosarcoma,
cancer metastases to bone, and hypertension.
Minimal Proteinuria (< 0.5 g/day)
¾ Following exercise or in highly concentrated urine, in
¾ Fever, severe emotional/thermal stress, in otherwise
¾ Postural proteinuria; young adults may pass protein
while ambulatory but not while lying
¾ Renal tubular dysfunction, including genetic and druginduced
¾ Lower urinary tract infections
¾ Hemoglobinuria with severe hemolysis.
Moderate Proteinuria (0.5–3 g/day)
¾ Chronic glomerulonephritis—moderate
Marked Proteinuria (> 3 g/day)
¾ Chronic glomerulonephritis—severe
¾ Severe diabetic } and other causes of
nephropathy nephrotic syndrome
Nonrenal Causes of Proteinuria
¾ Poisoning from turpentine, phosphorus, mercury,
sulfosalicylic acid, lead, phenol, opiates and drug
FIG. 5.2: Esbach’s albuminometer
¾ Large numbers of leukocytes accompanying proteinuria
usually imply infection at some level in the urinary
tract. Large numbers of leukocytes and erythrocytes
usually indicate a non-infectious inflammatory disease
of glomerulus. Proteins with pyelonephritis may have
as many RBCs as white blood cells.
¾ Proteinuria does not necessarily always accompany
cause severe illness without causing protein leakage.
¾ Proteinuria is associated with the finding of casts on the
sediment examination as protein is necessary for cast
¾ Postural proteinuria is the excretion of protein by
patients who are standing or moving during daytime.
This proteinuria is intermittent and disappears when
the patient lies down. Postural proteinuria has an
incidence of 3 to 5% of all normal healthy subjects.
Collecting Specimen for Orthostatic Proteinuria
1. Instruct the patient to void at bedtime and discard
2. Next morning sample is collected immediately as the
patient awakes and assumes a standing posture.
3. A second specimen is collected after the patient has
been standing or walking for a considerable period of
Differentiation from other types of proteinuria is
done by testing for protein in two urine specimens; one
collected before and one after the person is erect. In
postural proteinuria the first sample would be devoid of
protein while second one would be positive.
a. Functional, mild and transitory protein in the urine,
because of renal vasoconstriction, is associated with:
b. Increased protein in urine occurs:
• After eating large amounts of protein
• In pregnancy or immediately following delivery
c. False or accidental proteinuria may occur because of
a mixture of pus and RBCs in urinary tract infections
d. False positive results can occur from incorrect use and
assessment of color strip test.
• Prolonged dipping or allowing the strip to be
held too long in the urine stream.
• Failing to accurately match the reactive area with
e. Alkaline urine can give a false positive test on the color
strip test due to alkaline, highly buffered urine.
f. A very dilute urine may give a falsely low protein value.
g. Drugs that may cause false positive tests for protein
(acid turbidity methods only) include:
• Radiopaque contrast media for up to 3 days (no
false positives with dipsticks, only with sulfosalicylic acid test)
• This list includes many other drugs also.
a. Glomerular proteinuria: There may be increased
filtration of plasma proteins when there is disruption of
normal glomerular capillary permeability—as occurs
with antigen-antibody, with infiltrative processes such
as amyloid or with ischemic glomerular injury.
b. Tubular proteinuria: There is increased renal
excretion of plasma protein in the presence of normal
glomerular permeability—increased filtered load
of small proteins, light chain proteinurias, multiple
Normal filtered load of small proteins with a
decreased capacity for tubular absorption of these
proteins—chronic cadmium poisoning, Fanconi’s
syndrome, cystinosis, and some patients with Wilson’s
c. Postglomerular proteinuria: There is secretion of
protein by the structures of upper and lower urinary
tract—in response to infection or the presence of renal
Microalbuminuria is the earliest sign of nephropathy
before it manifests overtly as proteinuria, a condition
where significant kidney damage has already occurred.
Microalbuminuria is classified as:
¾ Albumin excretion rate: 20–200 µg/min or 30–300 mg/day
¾ Albumin/Creatinine ratio: 2.5–25 mg/mmol
¾ Albumin/ Creatinine ratio: 30–300 mg/g
¾ Albumin concentration (early morning urine): 30–300
Microalbuminuria can only be detected by specific
immunochemical assays for urinary albumin using
antibodies to human albumin. The existing biochemical
tests for detection of microprotein are nonspecific as they
also detect other proteins apart from albumin.
Although dye binding and protein precipitation assays
have been described, these are insensitive and nonspecific
Microalbuminuria: Diagnostic Relevance
Microalbuminuria indicates high probability of damage
of the glomerular filtration capacity of the kidney and is of
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