BIOCHEMICAL TESTS Biochemical tests are ordered to diagnose

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

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 �CO 2 �Chloride �Blood urea nitrogen �Creatinine

Gomprehensive Metabolic Panel (CMP) Includes: �Glucose �Calcium �Sodium �Potassium �CO 2 (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 -I 45 m. Eq/L 3. 6 -5 m. Eq/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. 2 mg/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/d. L 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 <8 mg/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 B 12 Red blood cells 3 -5. 9 x 10 6/mm 3 (men) 3. 5 -5. 9 x 106/mm 3(women) White blood cell count (WBC) 5 -10 x l 03/mm 3 (>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 p. H 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 4 g 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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