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Basic Concept of Clinical Biochemistry


Academic year: 2023

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Clinical biochemistry is one of the most rapidly advancing fields in laboratory and clinical medicine. Sensitivity is the ability of an analytical method to detect small amounts of the measured analyte. Analytical methods require calibration, the process of relating the value indicated on the scale of the measuring device to the quantity to be measured.

The test results can be compared with the results of the same tests previously performed on the patient. Automation may initially incur high costs for the acquisition of equipment, but it is economical in the long run due to the reduction of manpower required to perform tasks. Single-channel analysis (single test analysis) each sample is analyzed with one procedure.

Each of the samples is subjected to several analytical processes and sets of test results are obtained. Chemical reaction: The samples undergo chemical reactions in the analyzers in the presence of appropriate reagents and optimal conditions. The disadvantage of the use of oxalate is the change in concentrations of plasma components.

Face barrier protection should be used if there is a significant potential for splashing of blood or body fluids. Capillary blood can be collected from the tip of the thumb or finger or from the earlobe. Urine is an excretory product of the body and the presence of certain substances in urine reflects the metabolic state of the body.

Fig. 3: Autoanalyzer
Fig. 3: Autoanalyzer

Glucose / Reducing Substances

Normal adults excrete up to 150 mg of protein/day (5 to 15 mg Albumin, 50 to 70 mg Tamm Horsfall mucoprotein, a product of the epithelial lining of the tubules, and the remainder various plasma proteins or glycoproteins). Nephrotic syndrome is a clinical condition when the kidney loses more than 3.5 gm protein/day/1.73 m2 with hypoalbuminemia, edema, hyperlipidemia, lipiduria, and hypercoagulability.

Ketone Bodies






For Proteins

If the precipitate is due to proteins, it will increase with acidification, and if it is due to phosphates, it will dissolve again.

For Sugars

For Blood/Haemoglobin

For Ketone bodies

For Bile Salts Hay’sTest

For Bile Pigments Fouchet’sTest

The total volume of CSF is about 150 ml, and the production rate of CSF is about 550 ml per day, so the turnover rate is about 3.7 times per day. CSF is reabsorbed into the venous system by numerous microscopic arachnoid villi and larger but less common arachnoid granulations (corpuscles of Pacchini). Villi and granulations are outgrowths of the arachnoid membrane that pierce the gaps in the dura and protrude inside the venous sinuses.

These projections act as valves, allowing a one-way bulk, flow (direct flow) of CSF into the venous blood, approximately 500 ml per day with additional amounts by diffusion in cerebral blood vessels and through the cribriform plate of the ethmoid bone in the nose. A blood CSF barrier exists for many substances such as bilirubin and certain drugs, so their concentration in CSF is lower than in plasma. The composition of CSF is essentially the same as that of brain ECF and is largely determined by the cell surfaces on which it is produced (choroid plexus), where it is absorbed (arachnoid villi and pacchinian granulation).

Active transport in and out of the CSF space is likely responsible for maintaining this difference. A wide range of disorders can cause alteration in CVS composition and the type and magnitude and extent of alteration are often not specified for a single pathological condition. CSF is collected by lumbar puncture in which a fine bore needle (22 or 24 L.P needle) is inserted between the 3rd and 4th lumbar vertebrae into the subarachnoid space with the patient lying in the lateral position and the fluid allowed to flow automatically.

The bevel of the needle must be parallel to the long axis of the spine. Appearance: Normal CSF is clear and colorless and produces no coagulum or sediment on standing. When hemolysis occurs in the CSF, the released hemoglobin is converted to bilirubin and this gives a yellow color to the CSF. more visible after centrifugation) called xanthochromia.

An increase in total proteins is the most common chemical abnormality in CSF and results from a breakdown of the blood CSF and brain-CSF barriers usually as a result of an inflammatory response, but sometimes if the flow of CSF is obstructed . If the permeability of the barriers is noticeably increased, fibrinogen is present which forms a clot or coagulum in the test tube. Pandy's test: 2 drops of CSF are added to 2ml reagent (10g phenol + 150ml water) and the degree of opalescence is noted - slight opalescence, opalescence, marked opalescence or turbidity.


Renal function tests are specialized tests and are advised when the medical history, examination and routine tests such as urinalysis suggest any kidney disease. Drug dosage may need to be adjusted if renal function is abnormal. Renal function tests: Renal function tests can be grouped into (a) those that assess glomerular function and (b) those that study tubular function.

Renal function tests do not provide any information about structural integrity or structural pathology. The functional unit of the Kidney is the nephron, which consists of the Glomerulus, the Proximal Convoluted Tubule (PCT), the loop of Henle, the Distal Convoluted Tubule (DCT) and the collecting tubule. Quantification of total kidney function is based on the assumption that all functional nephrons are functioning normally and that a decline in kidney function is due to complete functional loss of nephrons and not due to impaired nephron function.

Renal tubules make up 95% of the kidney's mass, perform most of the metabolic work and convert the ultrafiltrate into urine. Clearance: Clearance of matter is the volume of plasma, cleared matter per unit of time. GFR is the most sensitive and reliable parameter for assessing glomerular function. a) Inulin - inulin clearance is an accurate reflection of GFR (inconvenient - requires intravenous infusion).

Procedure for Creatinine Clearance Test: Give the patient 500 ml of water to increase urine flow. The importance of determining creatinine clearance lies in the early detection of functional kidney impairment without obvious signs and symptoms. The creatinine clearance test is useful in the long-term monitoring of patients with renal insufficiency on a protein-restricted diet, creatinine clearance is modified by body muscle mass, medications, age, sex, and the nature of the diet.

The most famous formula is the Cockcroft-Gault formula, which is relatively simple to use and quite accurate. Urea clearance is the number of ml of blood containing urea that is excreted by the kidneys in one minute. Interpretation of urea clearance value: If the value is below 75% of normal, it is considered abnormal.


Fig. 3: Autoanalyzer
Fig. 5 Pipettes: Demonstration of how to use a pippete
Fig. 4: Vacutainers used for blood collection and storage
Fig. 6: Safety measures to avoid hazards


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