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183
Interpretation of Clinical Laboratory Tests
Capillary blood methods:
a. Slidemethod:2–6minutes
b. Capillarytubemethod:2–6minutes
Venous blood methods:
a. Howellmethod:0–30minutes
b. LeeandWhitemethod:5–15minutes
Clinical Significance: Clottingtimeisprolongedinhaemophilia,vitaminKdeficiency,
obstructivejaundice,dicoumaroltherapy,heparintherapy,pneumoniaandleukaemia.
Thepresenceofheparinprolongsthecoagulationtime.Hence,thistestissignificantly
importantincontrollingthetherapeuticactionofthisdrug.
5. Blood Sugar
Blood glucose test determines the glucose (sugar) level in the blood. Glucose is generated
from metabolism of carbohydrate taken in foods. Carbohydrate is the main source of
energy used by the body. Insulin is a hormone that is responsible for the utilization of
glucose by the cell. Insulin is formed in the pancreas (endocrine gland) and released
into the blood in response to rise in sugar level. After ingestion of food, blood glucose
level increases slightly. The rise in sugar level stimulates the pancreas to release insulin
to utilize the sugar, thus rise in blood sugar level is prevented. The sustain rise in blood
sugar level leads to diabetes, that can cause the complication in eyes, kidney function,
nerves, and blood vessels.
Normal range of blood sugar level: 80–120 mg/100 ml or dl.
The above and below level of sugar in comparison to normal level are termed as
hyperglycaemia and hypoglycaemia respectively.
Various Types of Blood Sugar Tests
Fasting blood sugar (FBS) test: It measures blood glucose after avoiding eating for least
8 hours to check for prediabetes and diabetes respectively.
Normal range: 72 to 125 mg/dl
2-Hour Postprandial (PP) Blood Sugar:The word‘Postprandial’ means after food.
Thistestisdonetocheckthebodyresponseaftertakingfood.Thebloodsugarlevel
ismeasuredexactlyafter2hoursaftertakingfood(atleast75 ‘g’ofcarbohydrates).
Normalvaluesforthe2-hourPPtestare:
• Lessthan140mg/dlinnon-diabeticperson
• Lessthan180ml/dlindiabeticperson
Random Blood Sugar: This test determines theblood sugar level at anytime. The
measurementdoesnotrequirefastingoringestionofcarbohydrates.Asglucoselevels
inhealthypersondonotchangeappreciablythroughouttheday,randomsugartest
canbehelpfultoidentifyhyperglycaemia.Randombloodglucosedeterminationcan
behelpfultoidentifyhyperglycaemiaanddecreasetheriskforsomechronicproblems.
Determiningbloodsugar level severaltimesin a daycanbe helpful tomanagethe
diabetestominimizethecomplicationsassociatedwithdiabetes.
Normal value: At 2 hours, a blood sugar level of 140 mg/dl or lower is considered
normal, 140 to 199 mg/dl suggests prediabetes, and 200 mg/dl or more suggests
diabetes.
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Oral glucose tolerance test (OGTT): PrediabetesanddiabetesareconfirmedbyOGTT
test.Itdetermines,howwellthebodycandealwithalargeramountofsugar.Forthistest,
seriesofbloodglucosemeasurementsismadeaftertakingadrinkaliquidcontaining
acertainamountofglucose(usually75g).Thistestisspecifictodiagnosegestational
diabetesthatoccursduringpregnancy.
Higher than 190 mg/dl after the one-hour test, indicates gestational diabetes.
Glycohemoglobin A1c test: It is also called the glycated haemoglobin, glycosylated
haemoglobin, haemoglobin A1c or HbA1c test. This A1c test determines what % of
haemoglobin proteins in the blood are coated with sugar (glycated). Normally, only 4 to
6 % haemoglobin in the blood has glucose molecule bound to it. Diabetic person has more
glycated haemoglobin than normal due to elevated blood sugar level. The higher A1c level
indicates the poorer blood sugar control and the higher risk of diabetes complications.
It also indicates how well diabetes has been controlled in the last 2 to 3 months and whether
change in diabetic medicines is required or not. HbA1 test determines the average blood
sugar levels during the last 3 months; common test to diagnose prediabetes and diabetes,
and is also useful for physician to assess the diabetes in patient.
Less than 5.7% is a normal value of test, while prediabetic and diabetic persons has
range of 5.7–6.4% and 6.5% and higher respectively.
6. Lipid Profile
Lipids, fat-like substances are important constituents of cells and act as sources of energy.
Healthy levels of these lipids are monitored to determine abnormalities in healthy state.
Typical lipid profile includes:
Total cholesterol: This is a
determination of the total amount
of cholesterol in the blood, including
both low-density lipoprotein (LDL)
cholesterol and high-density lipoprotein (HDL) cholesterol.
High-density lipoproteins cholesterol (HDL-C): These are referred to as ‘good
cholesterol’, which determine the cholesterol in HDL particles. These are helpful in
elimination of excess cholesterol by transporting it to the liver for removal.
HDL cholesterol ranges from 40 to 60 mg/dl in healthy state.
Less than 40 mg/dl for men and less than 50 mg/dl for women are associated with
increased risk.
Low-density lipoproteins cholesterol (LDL-C): Thesearereferredtoas‘badcholesterol’,
whichdeterminesthecholesterolinLDLparticles.Thesecausesthedepositionofexcess
ofcholesterolinbloodvessels,whichisresponsibleforatherosclerosis.
Normal range for LDL cholesterol varies from 70 to 130 mg/dl in healthy state. More
than 130 mg/dl indicates the high LDL-C associated with risk factor.
Triglycerides: Analyse completetriglycerides intotal lipoproteinparticles. Most of
them are associated with very low-densitylipoproteins (VLDL). Desirable normal
triglyceridesrangeliesbetween10and150mg/dl.
Some other parameters, calculated from the results of the tests as illustrated above,
may be included in the lipid profile. For example,
Total Cholesterol
Less than 200 mg/dl Desirable healthy state
200–240 mg/dl Borderline high cholesterol
240 mg/dl or higher High level of cholesterol
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Interpretation of Clinical Laboratory Tests
Very Low-Density Lipoprotein Cholesterol (VLDL-C): VLDL cholesterol is usually
measured as a percentage of triglyceride value. Determined by dividing the triglyceride
value by 5.
VLDL-C = Triglycerides/5
This formula is based on the typical make-up of VLDL particles. Its desirable range is
below 30 mg/dl. Elevated VLDL cholesterol level is more than 30 mg/dl indicates risk
for heart disease. The best way to lower VLDL cholesterol is to lower the triglycerides.
Clinical Importance
High cholesterol level is designated as hypercholesterolemia. It is due to presence of
higher concentrations of LDL and lower concentrations of functional HDL. It assists in
atheroma development in arteries (atherosclerosis), which is associated with development
of cardiovascular disease. This may lead to myocardial infarction (heart attack), stroke,
and peripheral vascular diseases. Depression, cancer, and cerebral haemorrhage are
associated with low levels of cholesterol, referred to as hypocholesterolaemia.
7. Liver Function Profile
Levels of certain enzymes and proteins in the blood is determined in liver function test.
Higher or lower levels than normal can indicate liver problems. Enzymes and protein,
which are determined in common liver function test comprise of:
ALT or alanine transaminase: ALTisanenzymeavailableintheliverthatconverts
alanineintopyruvate,forcellularenergyproduction.Normally,ALTlevelsintheblood
arelowbutincaseofliverdamage,levelsriseduetoincreaseinrelease.
Reference range: 7–56 units/L
AST or aspartate transaminase: AST is also known as serum glutamic-oxaloacetic
transaminase, or SGOT. It is an enzyme that aids in metabolism of alanine (amino acid).
Like ALT, AST is normally present in blood at low levels but its levels increase in liver
damage or infection or muscle damage.
Reference range: 10–40 units/L
Normal range of AST and ALT may slightly vary depending on the individual
laboratory’. Usually, reference range for AST and ALT varies from 10 to 40 units per
litre and 7 to 56 units per litre respectively. The value which is 2–3 times higher than
the reference range is considered mild elevations but if in range of 1000s, there is severe
liver complications.
ALP or alkaline phosphatase: ALP is an enzyme, which is mostly available in the liver,
bones, kidney and digestive tract. Its elevated level is a suggestive of liver damage or
complications, such as a blockage of bile ducts, or certain bone disorders (like rickets,
osteomalacia, Paget’s disease).
Reference range: 45–110 units/L
Albumin and total protein: Albumin is one of the diverse proteins formed in the liver.
It is required to fight infections and to carry out various other functions in the body.
Various hormones, vitamins, and enzymes are also transported through albumin in the
body. Low albumin level in comparison to normal levels can be a sign of liver or kidney
disorders or another medical complications.
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Textbook of Pharmacy Practice
Normal range: 3.5–5.2 g/dl
Albumin and globulin levels are determined in the total protein test. Normal range
for total protein lies between 6 and 8.3 g per dl. This range may depend on some factors
such as age, sex, community, analysis method and individual laboratory.
Bilirubin: Breakdown process of RBCs is responsible for the production of bilirubin,
which passes through the liver and eliminated via stool. High bilirubin levels can result
from liver disorders, pancreatitis, some cancers, and certain types of anemia.
Reference range: 0.1–1 mg/dl
GGT or gamma-glutamyl transferase: Serum GGT enzyme is an indicator of liver
dysfunction and marker of alcohol intake.
Normal range: 50–420 IU/L
LDH or lactate dehydrogenase: It is determined to check the tissue damage, liver
damage and some other diseases can be diagnosed with its elevated levels.
Normal LDH range: 140–280 units/L
PT or prothrombin time: PT is a blood test that determines the time it takes for the blood
to clot. Elevated PT may suggest the liver injury. The elevated PT is also observed with
the intake of certain blood-thinners, such as warfarin. Generally, results are indicated
as INR (international normalized ratio).
Normal range for PT is: 11 to 13.5 seconds. INR is 0.8 to 1.1.
Clinical Importance
Liver function tests are most often used to:
• Diagnoseliverinfections,suchashepatitis.
• Monitortheprogressionofadisease,suchasviraloralcoholichepatitis.
• Monitorthetreatmentofliverdisease.
± Assesstheseverityofadisease,particularlydamageoftheliver(cirrhosis).
± Monitorexpectedsideeffectsofantibiotics.
8. Kidney Function Profile
Common kidney function tests include the determination of:
Uric Acid: Uric acid is created, when the body breaks down purines in human body.
Normal reference value in adult male is 2–6 mg/100 ml, which is slightly lower in
females.
Clinical Importance
High blood uric acid level (also known as hyperuricemia), is observed in:
• Renaldisorders
• Leukaemia
• Metabolicacidosis
• Obesity
• Polycythaemiavera
• Psoriasis
BUN or blood urea nitrogen: Duringmetabolism,the proteins arebrokendown to
aminoacidsanddeaminated.Theammoniageneratedinthisprocessisconvertedinto
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Interpretation of Clinical Laboratory Tests
ureain theliver,whichisexcretedinurine.Thisis the mostimportantpathwayfor
eliminatingexcessofnitrogenfromthehumanbody.Theresponsibilityofeliminating
theureadependsonhowwellkidneysareworking.The7–25mg/dlisnormalblood
rangeofBUN.
Clinical Importance
Generally, elevated BUN levels are observed if kidneys are not functioning well. But
there may be several other reasons for elevated BUN value, such as dehydration, urinary
tract blockage, CHF, gastrointestinal bleeding, shock, severe burns, etc. It is also elevated
due to intake of proteinaceous food (meat, poultry, fish, eggs, and dairy foods).
Serum creatinine: Creatinineisanon-proteinnitrogenouswasteproductgeneratedin
muscle.Creatinineisformednon-enzymaticallyfromcreatineinmuscle.Itisusually
producedatafairlyconstantratebythebody(dependingonmusclemass).
The reference range for women and men is 0.5 to 1.0 mg/dl and 0.7 to 1.2 mg/dl
respectively. It is the most commonly used marker of renal function. Elevated blood
creatinine level is observed only in marked impairment in functioning of nephrons.
BUN/creatinine ratio: BothBUNandcreatinineareexcretedoutthroughthekidney.
Hence,ratioofBUNandcreatinineisdeterminedtopredictkidneyfunction.
The ideal ratio of BUN to creatinine lies between 10 :1 and 20:1.
GFR or glomerular filtration rate: Itisthevolumeoffluidfilteredfromthekidney's
glomerularcapillaries perunit time. This test measures,how well the kidneysare
performingfor eliminationof waste product andexcess fluid from theblood. It is
calculatedfromtheserumcreatininelevelby isotope dilutionmassspectrometry, it
canbecalculatedfromtheserumcreatininelevel.
Normal value for GFR is 90 or above. GFR below 60 signifies that the kidneys’ function
is not proper. If GFR falls below 15, person is at high risk and has the requirement of
treatment for kidney failure, such as dialysis or a kidney transplant.
9. Carbon Dioxide (CO
2
) Test
Carbon dioxide level in the blood is estimated by this test. Most of the carbon dioxide
is available in body as bicarbonate, regulated by the lungs and kidneys.
Reference range: 24–30 mEq/L
High level of carbon dioxide signifies metabolic alkalosis, or presence of too much
bicarbonate in blood, Cushing disease, hyperaldosteronism, etc.
Low carbon dioxide level means metabolic acidosis, ketoacidosis (observed in type 1
and type 2 diabetes), lactic acidosis, etc.
10. Electrolytes and Minerals Tests
Cl or Serum Chloride test: Chloride level in the blood is determined by this test.
There may be change in chloride levels in case dehydration or overly hydration, renal
impairment. Abnormal chloride levels are also observed in heart failure and some
endocrinal problems.
Reference range: 100–106 mEq/L
K or serum potassium test: The potassium level in the blood is determined with this
test. Both high and low potassium levels can result in complications related to rhythm
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of the heart, so it is essential to monitor the potassium level after surgery. Patients who
are taking diuretics regularly, may require monitoring of potassium levels, as some
diuretics mechanistically guide the kidneys to excrete too much potassium.
Reference range: 3.5–5 mEq/L
Na or serum sodium: Thistestdeterminesthelevelofsodiumpresentintheblood.The
kidneysexcreteexcessofsodium,ingestedthroughfoodandbeverages.Sodiumlevels
goupanddownwithdehydrationorover-hydration,intakeofthefoodandbeverages,
dysentery,endocrinalproblems,waterretention,injuryandbleeding.
Reference range: 135–145 mEq/L
Serum calcium (Ca): Bloodcalciumtestisdonetoobserve,diagnose,andmonitora
rangeof circumstancesrelatingto the bones,heart, nerves,kidneys, and teeth. The
testmay also berecommendedif apersonhas symptomsof a parathyroiddisease,
malabsorption,orahyperactivethyroid.
Reference range: 4.5–5.5 mEq/L
Serum Phosphorus (P): Formakingthestrongbonesandteeth,phosphorusisessential
element,requiredbythebody.Itisalsoessentialfortransmissionofnerveimpulseand
muscle contraction. Hyperphosphatemia (highphosphorus level) may occur due to
varioushealthconditions,diabetes,ketoacidosis,hypoparathyroidism,kidneyfailure,
liverdisorders,toomuchintakeofvitaminD,etc.Hypophosphatemia,indicativeoflower-
than-normalbloodlevelofphosphorous,mayoccurduetoalcoholism,hypercalcemia
(toomuchcalciuminthebody),hyperparathyroidism,intakeoftoolittlevitaminD,etc.
Reference range: 2.4–4.1 mg/dl
11. Thyroid Blood Tests
Thyroid blood test is done to analyse the proper functioning of thyroid gland by
measuring the blood level of thyroid hormones. Thyroid gland related diseases are
diagnosed with thyroid test. Through the thyroid test, physician is able to diagnosis
various thyroid diseases such as:
• Graves’disease(occursduetohyperthyroidism)
• Hashimoto’sdisease(occursduetohyporthyroidism)
• Thyroidnodulesandthyroidcancer
TSH Test: TSHisahormone,generatedinthepituitaryglandthatguidesthethyroid
gland,howmuchT
4
andT
3
toproducetomeettheneedofthebody.
High TSH level suggests hypothyroidism, or an underactive thyroid. If thyroid gland
is not making sufficient thyroid hormones, it means, the pituitary gland keeps releasing
TSH into the blood to stimulate the gland.
Low TSH level usually recommends the existence of hyperthyroidism, or an
overactive thyroid gland. This indicates that thyroid gland is making too much thyroid
hormones, so the pituitary gland is not releasing TSH into the blood.
If the TSH test results are not normal, there is need of at least one other test to help
find the cause of the problem.
Reference test range (Adult male): 0.4 to 4.0 mIU/L
T
4
Tests: High and low bloodlevel of T4 may indicates hyperthyroidism and
hypothyroidismrespectively.
189
Interpretation of Clinical Laboratory Tests
In some cases, thyroid problems are not confirmed with the high or low T
4
levels.
For example, in pregnancy or with the intake of oral contraceptives, level of thyroid
hormone becomes increased. Severe illness or using corticosteroids to treat asthma,
arthritis, skin inflammation, etc can cause lower T
4
levels in blood.
Reference range: 5.0–11.0 µg/dl.
T
3
test: IfpatienthashyperthyroidismeventhoughT
4
levelisnormal,thenphysician
mayrecommendfortheconductofT
3
testtoconfirmthediagnosis.Sometimes,T
4
is
normal,yetT
3
ishigh,sodeterminingbothT
4
andT
3
levelscanbebeneficialinthe
diagnosisofhyperthyroidism.
Reference range: 100–200 ng/dl.
Thyroid Antibody Tests
Determination of blood levels of thyroid antibodies may be helpful in diagnosis an
autoimmune thyroid disorder such as Graves’ disease (occurs due to hyperthyroidism)
and Hashimoto’s disease (occurs due to hypothyroidism). Thyroid antibodies are
formed, when body own immune system attacks the thyroid gland by fault. For this
reason, physician may recommend for thyroid antibody tests if other blood tests point
out for the presence of thyroid disease.
TESTS ASSOCIATED WITH CARDIAC DISORDERS
There are two types of processes:
Non-invasive Process
1. Chest X-ray: Itisusedforthediagnosisoftheheartenlargementandaboutitssize
andshape.
2. ECG: Bythistechnique,theelectricalactivitiesoftheheartarestudied.Graphicalrecord
ofelectricalchangesoccurringduringthecardiaccycleoftheheartisknownasECG.
3. Echocardiography: Using the ultrasound, thiscan investigateand visualize the
heart,structuralanatomy,size,andmotion.
4. Magnetic resonance imaging (MRI) scan: Inthistechnique,astrongmagneticfield
andveryhighfrequencyradiowavesareusedtogeneratedetailedimagesofvital
organslikeheart.Itprovidesdetailedpictureofheartandbloodvessels,usefulfor
diagnosingcongenitalabnormalities,abnormalgrowthandtumours.
Invasive Process
It means, incision of the body by the external subject.
1. High speed computed axial tomography: Bythistest,cardiologistcandetectcardiac
functionandcardiacstructure.Itprovidesprecisevisualizationofcardiacstructure
fromtheinnerendocardialwalltosurfaceofthepericardium.
2. Common serum enzyme test: Varioustypesofenzymescirculateinthebloodall
times.Tissuedamagecausesthereleaseoflargequantityofenzymeinblood.Hence,
enzymelevelisusedindiagnosisofcardiacdisorders.Forexample
a. Creatinine kinase (CK): Also known as creatinine phosphokinase (CPK) or
phosphocreatinekinase,itisanenzymeexpressedbyvarioustissuesandcelltypes.
CKcatalysestheconversionofcreatinineandusesATPtocreatephosphocreatinine
(PCr)andadenosinediphosphate(ADP).Itslevelisevaluatedtodetectmyocardial
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infarction(MI) (commonlycalled heart attack) and monitorthe seriousness of
myocardialischemiaaftercardiacsurgery,cardiaccatheterization.
Normal value:
Adult man: 55–170U/L
Adult female: 30–135U/L
b.Lactate dehydrogenase: ItslevelisusedtodetectMI,pulmonaryinfarction.There
arefiveenzymes:LDH1,LDH2,LDH3,LDH4,andLDH5.
Normal:71–207U/L
LD1: 14–26%
LD2: 29–39%.InMI,LD1willbehigherthanLD2.SoLD1/LD2isgreaterthan1
c. Troponin: Troponinisatypeofproteinfoundinthemusclesoftheheart.Troponin
isnot normally found in the blood. When heartmuscles become damaged,
troponinisreleasedintothebloodstream.Hence,inheartdamage,highlevel
oftroponinisobservedintheblood.
Highlevelsoftroponininthebloodmaymeanthatpatientishavingorrecently
hadaheartattack.
Reference range: 0to0.04ng/ml
Probable heart attack: Above0.40ng/ml
d. Aspartate aminotransferases:Theseenzymesareprimarilyfoundinheartand
liver. In heart attack,AST level is increased.Its levelalso increasesin acute
hepatitis,cirrhosis,fattyliverandcongestionofliver.
STOOL EXAMINATION
The healthy adults generally defecate at least once in a day. Depending on intake of diet,
stool tends to be soft and bulky. Two-thirds of the stool weight is accountable for its
water content. Reason for normal brown colour is still not clear. The bad smelling odor
is due to presence of indole and its derivative, 3-methyl indole (skatole). The skatole is
white crystalline organic compound, which is mild toxic in nature. It is produced from
metabolism of tryptophan in the digestive tract.
Clinical Importance
In stool examination, series of tests are performed to diagnose certain conditions affecting
the digestive tract. These conditions can be parasitic, or bacterial, deficient dietary
nutrient absorption, obstructive jaundice, diarrhoea, dysentery or ulcerative colitis or
cancer. Generally, there are two types of examinations—macroscopic and microscopic
examinations. There may be chemical examination, include in stool examination.
Macroscopic Examination
In this test, the form, consistency and colour of stool are observed.
Type of stool Probable reason
Watery stool Diarrhoea
Large amount of mushy, foul
smelling, grey stool which float
on water
Steatorrhea (presence of excess of fat in feces). Stool may foul smelling,
grey stool also floats due to excess lipid
(Contd.)
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Interpretation of Clinical Laboratory Tests
(Contd.)
Little firm, spherical masses Constipation
Narrow ribbon like stool Spasm in bowel or narrowing of rectum
Clay coloured Mechanically obstructive jaundice
Red coloured stool Blood from lower gastrointestinal tract
Black, tarry stool Bleeding in upper GI tract or due to intake of iron, bismuth or charcoal
Green stool Intake of spinach, other green vegetables, calomel, presence of
biliverdin is observed in patient taking antibiotics.
Mucous stool Chronic ulcerative colitis and bacillary dysentery
Microscopic examination
Cells RBCs, mucous and pus cells indicate amoebic dysentery and
macrophages, pus cells indicate bacillary dysentery
High levels of fat in the stool May occur in pancreatitis, celiac disease, cystic fibrosis, in which the
absorption of fats is affected.
Parasites and eggs Protozoans: Entamoeba histolytica and
Entamoeba coli, Trichomonas hominis, Giardia lambia (Giardiasis),
Balantidium coli (Balantidiasis)
Helminthes: Eggs are seen in Helminthes infestation
Chemical Examination
Stools may be slightly acidic, or alkaline or neutral, depending on pH values ranging
from 5.8 to 7.5.
i. Stronglyacidic stoolhas (pH below 5.5), dueto prevalenceof anexcess of
carbohydrates in the diet.It is non-pathologic, but becomes pathogenic due to
fermentation.Pathogenicconditionmayoccurduetolactoseintolerance.
ii. Stronglyalkalinestool,pHabove7.5,suggestanexcessofproteininthediet.Itis
non-pathologicinnature.
iii. Occultblood:Generally,notfoundbutifobserved,maybeduetoeitherinfection
orsomeabnormalitiesintheGItract.
iv. Reducing substances: These may appear in stools of infants, suffering from dysentery.
URINE EXAMINATION
Urinalysis (UA) is a significant laboratory examination to enable the clinician to diagnose
patients with renal disorders, as well as some nonrenal disorders. Gross appearance,
pH, specific gravity (SG), determination of protein, glucose, ketones, blood, bilirubin,
leukocyte esterase, nitrites, etc are included in UA.
Appearance
The normal urine colour ranges from clear to dark yellow. Urine is cloudy, may be due
to presence of phosphates or urate. The presence of WBCs, RBCs, or bacteria may also
increase the urine cloudiness abnormally. Abnormal colour of urine may be due to the
followings types:
• Red-orange colour:Duetopresenceofmyoglobin,haemoglobin,medications(e.g.
rifampicin),orfoods(e.g.beets,carrots,blackberries).
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• Blue-green colour: May be due to use ofamitriptyline or methylene blue, or
pseudomonalinfection.
• Brown-black colour: Maybeassociatedwithpoisoningwithphenol,oringestion
ofrhubarb.
Specific Gravity (SG)
Normal value: 1.005 to 1.025.
Specific gravity is an indication of the concentration of particles in urine, which is
function of the kidney. Unusually, low specific gravity suggests the inability of the
kidneys to concentrate urine appropriately.
Clinical Significance
Low specific gravity (hyposthenuria) may happen in chronic renal failure or diabetes
insipidus, while elevated specific gravity (hypersthenuria) may be associated with
dehydration, congestive heart failure (CHF), etc. In addition, enhanced elimination
of glucose or protein greater than 2 g/day through urine may also increase specific
gravity of urine.
pH
Normal values: 4.5 to 8.
Generally, urine is acidic in nature, with average pH value of 6.
Clinical Significance
Alkaline urine may be observed in certain UT infections, renal tubular acidosis, and
with the use of thiazide diuretics.
Metabolic acidosis, pyrexia, or diabetic ketosis increase the acidity in urine.
Protein
Trace amount of protein is found in the urine, which has no clinical significance.
Clinical Importance
High level of protein (proteinuria) (greater than 150 mg/dl) in urine is an indication of renal
disease, which may be due to diabetic nephropathy, interstitial nephritis, hypertension,
fever, exercise, pyelonephritis, multiple myeloma, lupus, and severe CHF.
Glucose and Ketones
Healthy person is devoid of both glucose and ketones in a urine but glucose shows
its appearance into urine (glucosuria), when serum blood glucose is greater than 180
(referred to as threshold).
Clinical Importance
Glucose in the urine signifies the presence of diabetes mellitus; may also be observed
in Cushing disease, pancreatitis, and use of thiazide diuretics, steroids, or oral
contraceptives.
Ketones intermediate metabolic products generated during metabolism of fat; also
generated, when body is deficient in carbohydrate source to produce energy.