Transcript biochemical tests

BIOCHEMICAL TESTS
Biochemical tests are
ordered to diagnose
diseases, evaluate treatment
plans, monitor medication
effectiveness, and evaluate
medical nutrition therapy
(MNT).
Biochemical assessment is a controlled
process. It involves analyzing control
samples, with predetermined analyte
concentrations, with every batch of patient
specimens.
The results obtained from the samples
analyzed with a particular batch of patient
samples must compare favourably with the
predetermined acceptable values.
Acute illness or injury can trigger dramatic changes in
biochemical test results, including rapidly
deteriorating nutrition status.
However chronic diseases that develop slowly over
time also influence these results.
Laboratory-based nutritional testing, used to estimate
nutrient availability in biologic fluids and tissues.
Single test results must be evaluated in light of the
patient's current medical condition, medications,
lifestyle choices, age of the patient, hydration status,
fasting status at the time of the specimen collection, and
reference standards used by the clinical laboratory.
Specimen Types
Ideally the specimen to be tested reflects the total
body content of the nutrient to be assessed.
The most common specimens for analysis for
nutrients and nutrient-related substances are the
following:
Whole blood: collected with an anticoagulant. if entire
content of the blood is to be evaluated; none of the
elements are removed; contains red blood cells, white
blood cells, and platelets suspended in plasma.
Serum: the fluid obtained from blood after the blood has
been clotted and then centrifuged to remove the clot and
blood cells.
Plasma: the transparent liquid component of blood,
composed of water, blood proteins, inorganic electrolytes,
and clotting factors
 Blood cells: separated from anticoagulated whole blood
for measurement of cellular analyte content.
 Erythrocytes (red blood cells)
 Leukocytes (white blood cells) and leukocyte
fractions
 Blood spots: dried whole blood from finger or heel prick
that is placed on paper and can be used for selected
hormone tests.
 Other tissues (obtained from scrapings or biopsy
samples)
 urine (from random samples):contains a concentrate of
excreted metabolites
 Faces (from random samples or timed collections):
important in nutritional analyses when nutrients are not
absorbed and therefore are present in fecal material
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Less commonly used specimens include the
following:
Saliva: is used to evaluate functional adrenal stress and
hormone levels
Nails: easy-to-collect tissue that may be of value in
determining exposure to toxic metals; usually a poor
indicator of actual body levels of nutrients
Hair: an easy-to-collect tissue that is usually a poor
indicator of actual body levels of nutrients; may have
value in determining exposure to toxic metals
Sweat: classically used for presence of cystic fibrosis
Type of Tests
 Measurement of the nutrient, its metabolite or some
other products in blood or urine
 Measurement of the activity of a vitamin-dependent
enzyme in erythrocytes.
 Measurement of an accumulated metabolite whose
disposal depends on a vitamin or mineral-dependent
enzyme.
Clinical Serum chemistry
panels
Biochemical tests are ordered as panels or groupings
of tests or as individual tests. The most commonly
ordered groups of tests are the Basic metabolic panel (BMP) and
 The comprehensive metabolic panel (CMP) that
include groups of laboratory tests defined by the
Centers for Medicare Services .
 The BMP includes eight tests used for screening, and
the CMP includes all the tests in the basic metabolic
panel and six additional tests.
Basic Metabolic Panel (BMP) Includes:
 Glucose
 Calcium
 Sodium
 Potassium
 CO2
 Chloride
 Blood urea nitrogen
 Creatinine
Gomprehensive Metabolic Panel (CMP)
Includes:
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Glucose
Calcium
Sodium
Potassium
CO2 (carbon dioxide, bicarbonate)
Chloride
Blood urea nitrogen
Creatinine
Albumin
Total protein
Alkaline phosphate (ALP)
Alanine aminotransferase( AIIT)
Aspartate aminotransferase( AST)
Bilirubin
Clinical chemistry panels used in conjunction with
health history physical examination findings,
anthropometric data, and dietary intake data can be
helpful in screening for nutrition-related health
conditions.
The Complete blood Count
 The CBC or analysis and description of the red blood
cells is often accompanied by a differential count,
which enumerates each of the specific classes of
leukocytes.
Urinalysis
The urinalysis test is used as a screening or diagnostic
tool to detect substances in the urine associated with
different metabolic and kidney disorders.
Constituents of the common serum
Chemistry panels
Analytes
Serum
electrolytes
Na+
K+
Reference
Range
135-I45 mEq/L
3.6-5 mEq/L
Significance
those receiving total parenteral nutrition or
who have renal conditions, chronic
obstructive pulmonary disease, uncontrolled
diabetes mellitus (DM),
Glucose
70-99 mg/dl
(fasting)
Fasting glucose >125 mg/dl indicates DM
Creatinine
0.6-1.2mg/dl
Increased in those with renal disease and
decreased in those with PEM (i.e., blood urea
n trogen/creatinine ratio >15:1)
Analytes
Reference
Range
Significance
Blood urea
nitrogen or
urea
5-20 mg urea
nitrogen/dl
1.8-7 mmol/L
Increased in those with renal disease and
excessive protein catabolism; decreased in those
with liver failure and negative nitrogen balance
Albumin
3.5-5 mg/dl
Decreased in those with liver disease or acute
inflammatory disease
Bilirubin
Total bilirubin
0.3-1.0 mg/dL
Increased in association with drugs, gallstones,
and other biliary duct diseases and hepatic
immaturity
Total calcium 8.5-10.5 mg/dl
Hypercalcemia, Hypocalcaemia
Phosphorous 3-4.5 mg/dl
(phosphate)
Hypophosphatemia associated with
hypoparathyroidism and Decreased intake
Total
cholesterol
<200
Decreased in those with protein-calorie
malnutrition, liver diseases and
hyperthyroidism
Triglycerides
40-160 mg/dl
(age and sex
dependent)
Increased in those with glucose intolerance or
in those who are not fasting
Vitamin D
<8mg/ml
Selenium
60120µg/L
Low as well as high levels predispose to osteoporosis.
Constituents the Hemogram:
complete Blood Count
Analytes
Reference Range
Significance
Haemoglobin
concentration
14-17 g/dl (men)
12-15 g/dl (women)
In addition to nutritional deficits,
may be decreased in those with
haemorrhage, marrow failure, or
Renal, not sensitive for iron, vitamin
B12
Red blood cells
3-5.9 x 10 6/mm3
(men)
3.5-5.9 x
106/mm3(women)
White blood cell
count (WBC)
5-10 x l03/mm3
(>2 yr)
Increased (leukocytosis) in those
with infection, and Stress, decreased
(leucopoenia) in those with PEM,
infections or who are receiving
chemotherapy or radiation therapy
Vitamin E
Expressed as a ratio to
cholesterol
Vitamin C
>3 mg/L
Copper
0.8-1.75 mg/L
Chemical Tests in a Urinalysis
Analytes
Reference Range
Significance
pH
6-8 (normal
diet)
Acidic in those with a high-protein diet or
acidosis and in those with a urinary tract
infection
Protein
2-8 mg/dl
Marked proteinuria in those with nephrotic
symdrome, severe glomerulonephritis
Glucose
Not detected
(2-10 g/dl
in DM)
Positive in those with DM; rarely in benign
conditions
Bilirubin
Not detected
Index of unconjugated bilirubin; increase in
those with certain liver diseases
Ketones
Negative
Positive in those with uncontrolled DM
Iodine
>100µg/L
Vitamin A- meassurement of serum/plasma vitamin A
RELATIVE DOSE RESPONSE (RDRT) TESTpercentage increases in vitamin A levels, 5 hours after a
small oral dose of 450-1000 µg of retinol is measured. the
post dose increases in serum vitamin A is inversely
related to vitamin A status, because in vitamin A
deficiency retinol binding protein(RBP) accumulate in
the liver and availability of exogenous vitamin A results
in holo RBP.
Raised circulating levels of Vitamin A, are maintained
depending upon the amount accumulated unbound RBP.
RDR greater than 20% is suggestive of vitamin A
deficiency.
Tests for Protein Energy Malnutrition
SERUM PROTEIN
The first indication of malnutrition is the lowering of
serum total proteins and serum albumin.
The normal albumin levels are 3.5-5.5 g/dl.
During PEM the levels may slow down to 2.0-2.5 g/dl.
Serum transferin <0.45 mg/ml suggest severe
malnutrition.
SERUM AMINO- ACID RATIO
This ratio of non- essential/ essential amino acids is very
sensitive at an early stage of PEM as also in kawashiorkor .
This test is not sensitive to marasmus.
SERUM AMINO ACID RATIO=
Glycine + Serine + Glutamine + Taurine
Leucine + Isolucine + Valine + Methionine
Normal mean value
Subclinical malnutrition
Frank kawashiorkor mean value -
1.5
2 to 4
5
URINARY HYDROXYPROLINE INDEX
Hydroxyproline index =
µ moles hydroxyproline / ml
µ moles creatinine/ml/kg body weight
In normal children the index is 4.7.
The index declines in kawashiorker and marasmus.
In growth retardation the index is <2.
Urinary creatinine height index
The measurement provides an approximate idea of the
musculature of the child.
Urinary creatinine height index=
mg creatinine/24 hours excreted by the malnourished
child
mg creatinine/24 hours excreted by a normal child of the
same height
Normal and recovery from PEM
- 1
Kwashiorkor and marasmic kwashiorkor - 0.24 to 0.74
Marasmus 0.33 to 0.85
Fasting Urinary Nitrogen and Creatinine Nitrogen
Ratio
Urea creatinine ratio = mg urea nitrogen/ml
mg creatinine nitrogen/ml
children eating diets low in protein show low ratios of
urinary urea to creatinine.
Assessment of Protein Catabolic Rate
Using Urinary Urea Nitrogen
The amount of urea nitrogen excreted each day can be used to
estimate the rate of protein catabolism.
The total protein loss and protein balance can be calculated
from the urinary urea nitrogen(UUN) as follows:
Protein catabolic rate(g/day) = [24-hour UUN(g) + 4]* 6.25
The value of 4g added to the UUN represents unmeasured
nitrogen lost in the urine, sweat, hair, skin, and faeces.
The factor 6.5 is used as nitrogen accounts for about one sixth
the weight of dietary protein.
Protein balance(g/day)= protein intake- protein catabolic rate.
Assessment Of Protein Using Blood Urea
Nitrogen.
BUN levels generally falls less than 8 mg/ dl means protein
intake is reduced.
Assessment of vitamins and minerals.
THERE ARE 3 GENERAL APPROACHES direct measurement of the vitamins and many trace
elements or derivative in body fluids by chemical and
biological means e.g, plasma ascorbic acid level.
 Indirect assessment of vitamins function as reflected in
enzymatic reaction under controlled conditions.
 Measurement that occurs as result of deficiency.
ADVANTAGES OF BIOCHEMICAL TEST
 These have excellent accuracy and objectivity
 Non-invasive in nature
 Easy to assay
 Measured with high specificity
 These are nutrient specific
ADVANTAGES OF BIOCHEMICAL TEST
 Expensive
 Age, sex, community differences are not included
 Time consuming tests
 Require trained and skilled personnel
 Cannot be applied on a large sacale.
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