Clinical laboratory professional specialized to external quality assessment (proficiency testing) schemes for Laboratory medicine and clinical pathology. Author/Writer/Blogger
This test is evaluated in different conditions and diseases such as nephrotic syndrome, liver diseases, kidney diseases, in a patient suspected of malnutrition, and patients severe burn. See also: Procedures for the collection of blood for hemotological investigations.
About 3 to 5 ml of blood is collected in a plain test tube and blood is allowed to clot to get clear serum. The blood sample is centrifuged for 5 to 10 minutes and the serum is separated for the test. The patient's serum is may be stored at 4° C which may be stable for 72 hours.
It is defined as a condition in which the level of albumin in blood/serum is lower than the normal values.
It is defined as a condition in which the level of albumin in blood/serum is higher than the normal values.
This hormone test is evaluated in different conditions, such as Hyperaldosteronism, Cushing's syndrome and Virilizing syndrome.
This is due to the diseases of the gland.
This is due to external factors which lead to under activity of the glands.
For the estimation of Cortisol level, patient's serum is required. 24-hour urine sample is also collected in a plastic container containing boric acid. The serum is stable for 2 days if kept at 2° to 8° C.
For catecholamines (Epinephrine and Norepinephrine), plasma in EDTA or heparin is needed. The sample is transported along with an ice-pack, centrifuged immediately at 4° C, and plasma is separated. Plasma is freeze until the test is run. 24-hour urine sample may also be collected in a plastic container containing 6 ml of 20% HCl and refrigerate during collection.
Estrogen can be estimated in serum. The blood sample is collected in a plain test tube, centrifuged immediately, serum is separated and refrigerated until the test is performed. 24-hour urine sample is also collected in a plastic container containing boric acid.
Aldosterone test can be done from the plasma (EDTA, citrate or heparin). Patient's blood serum may also be used for the test. Patient must be upright for 2 hours before the sample is taken. 24-hour urine sample is also collected in a plastic container containing boric acid.
It is also known as Biochemical Oxygen Demand (BOD). It is defined as the amount of oxygen consumed during the process of degradation and eventual stabilization of unstable organic substances by the biochemical activities of aerobic and other microbes. This degradation of the chemical complex is a desirable process and the final product is called stabilized wastewater. The aerobic bacteria consume oxygen during the process of oxidization of the organic and other oxidizable inorganic substances. The immensity of biochemical degradation depends on the population of bacteria. An actively growing population of bacteria will consume more oxygen to quickly decompose unstable complexes. Biological/Biochemical Oxygen Demand (BOD) is reduced with the decrease in the quantity of these complexes in the wastewater. Therefore, it can be surmised that BOD is directly proportional to the level of degradable chemical complexes; high concentration of chemical substances will result in the high BOD.
The BOD is a very useful measure of the efficiency of methods of wastewater treatment. A method in which amount of BOD reduced quickly is considered as most effective and efficient method. Therefore, exactly stabilized effluent, when discharge in the body of water, does not cause reduction of oxygen in the water.
It is a well-known fact that the wastewater should be treated properly and effectively before its disposal into receiving water bodies. Disposal of wastewater may be accomplished with or without treatment.
There are different methods available for the removal of microorganisms and stabilized the putrescible organic and inorganic chemicals in the wastewater. These methods are known as wastewater treatment methods. It is a very interesting fact that usually microorganisms are used to reduce the large burden of wastewater, which is organic matter. With few exceptions, wastewater treatment plants are integrated with physical, chemical and microbiological methods to concern with the different problems related to wastewater.
According to distinct types of treatment, they are divided into four types. Each type of treatment process has a special purpose, targeting the removal of all sources of materials and reducing the burden of microorganisms from the wastewater.
This process is mainly designed to remove the total solids from the wastewater by sedimentation and render it adequately free from pathogenic bacteria by chlorination. Initially, large objects are removed by bar screens from the wastewater flow. It removes a significant amount of particulate matter. The collected objects are then put into the grinder and released back into the wastewater flow.
The wastewater is then allowed to flow to a series of large primary settling compartments in which most of the organic matters and dense inorganic particles such as grit and sands are removed. Usually, there are two types of settling compartment, (a) grit compartment and (b) sedimentation tank or quiescent settling compartment. In grit compartment, wastewater flows very slow which permits large and heavy particulate matter to settle out. In the next step, the municipal and industrial wastes (particulate organic matters) in wastewater are removed in the sedimentation tank. In sedimentation tank, wastewater is allowed to stay for 1 to 3 hours during which most of the suspended organic matter settles out. The sedimented material is in the form of a semi-solid mass called sludge. The efficiency of sludge formation can be increased by the addition of various chemicals to coagulate the suspended particles which enhanced the sedimentation rate. The sludge is not allowed to remain in the bottom of sedimentation tank for a long period because of anaerobic bacteria produce gases during metabolism that tend to resuspend the settled material and increased the odor. Therefore, the sedimentation tank is equipped with scrapper mechanisms that occasionally removes the bottom sludge to a collection hopper. The underflow sludge becomes a waste product of the process. The remaining liquid portion of the wastewater which leaves the tank is called effluent.
To be continue...
There are certain bacteria which cannot be stained by Gram's method. In 1882, Paul Ehrlich developed a method of staining such type of bacteria. This method was named, and still known as acid-fast staining and the bacteria were named as acid-fast bacteria. In the same year, Ehrlich's method was improved by Zehil and Neelsen. Nowadays, Ziehl-Neelsen method is believed as most important differential staining procedure used for the identification of acid-fast species of Mycobacterium, Actinomyces, and Nocardia. There are many acid-fast bacteria which are pathogenic, such as M. tuberculosis (tuberculosis), A. israelii (actinomycosis), M. leprae (leprosis), and N. asteroides (nocardiosis).
Acid-fast bacteria may be defined as those cells which keep the color of the primary dye (carbol fuchsin) even after the process of decolorization by the acid-alcohol solution. Those bacteria which fail to do so are known as non-acid-fast bacteria.
Acid-fast bacteria are coated with a thick waxy material, mycolic acid, which makes the bacterial cells highly resistant to the penetration of dyes. The penetration of dye is promoted by using heat as mordant. The heat invades the dye through the waxy coat and into the cytoplasm.
Microscopic examination reveals acid-fast tubercle bacilli as short, straight or slightly curved bright red rods. Non-acid-fast cells appear blue.
In 1985, a Pakistani microbiologist, Abdul Mobin Khan developed a method for the staining of acid-fast bacteria. In this method, heating of flooded primary dye on smear is not required. However, initial fixing of the smear over the flame is necessary in order to increase the permeability of the cell wall and promote the newly formulated primary dye to penetrate the cell.
Sputum, body fluid, pus, or swab of cells taken from the location of an infection; a sample of bacteria grown and isolated in culture.
Microscopic examination reveals acid-fast tubercle bacilli as short, straight or slightly curved red rods while non-acid-fast bacteria as blue.
In 1883 (originally published in 1884), Dr. Hans Christian Gram (1853-1938) developed a technique for the classification of bacteria into two broad groups, Gram-positive and Gram-negative. It is the most important staining technique for the classification and differentiation of bacteria.
The Gram stain consist of four reagents; crystal violet (use as a primary dye), Gram's iodine (use as a mordant), ethyl alcohol (use as a decolorizer), and safranin (use as a counterstain). The Gram-negative, on the other hand, lose the primary dye (crystal violet) when decolorized and, thus, take the color of counterstain (safranin).
The Gram-reaction rely upon the chemical nature of the bacterial cell wall, especially the lipids which comprise 11-22% in Gram-negative cell wall and 1-4% in the Gram-positive cell wall. In the Gram-negative cell wall, the amount of lipids is very high, when the cell is dissolved in alcohol, it leads to the formation of large pores in the cell wall. The dehydrating result of alcohol cannot fill these pores which cause the liberate of primary stain making the cell colorless. Such cells take the color or counterstain (safranin). On the contrary, the amount of lipid is very low in the Gram-positive cell wall and easily dissolved by in ethyl alcohol, causing the formation of very small pores. These pores are further closed by the dehydrating effect of alcohol which does not permit the primary dye (crystal violet) to leave the cell.
Identification, differentiation, and classification of the bacteria.
The Gram-positive bacteria appear in purple color and Gram-negative bacteria appear in pink color.
Sputum examination refers to the laboratory examination or test of the material or substance coughed out from the lungs, bronchi, trachea, and larynx. Normally, sputum is mainly composed of mucus and also certain cellular and non-cellular components of host origin. During expectoration, sputum gets contaminated with normal bacterial flora and cells from pharynx and mouth.
Waste products discharged from the digestive tract are composed of up to 75% water, food which is digested but not absorbed, indigestible residue, undigested food, epithelial cells, bile, bacteria, secretion from the digestive tract and inorganic bacteria. Normally an adult human excretes 100-200 grams of feces in a day.
Examination of stool is very helpful in the diagnosis of disease of the gastrointestinal tract as listed below.
Stool examination is performed for the detection and identification of worms (adult worms, larvae, segments of worms, ova) and protozoa (cyst or trophozoites). See also: Microscopic Examination of Feces
Stool culture is performed for the evaluation of bacterial infection such as Clostridium difficile, Yersinia, Salmonella, Shigella or Vibrio. Bacterial toxins (such as those released by Clostridium difficile or Clostridium botulinum) can also be identified. See also: Microscopic Examination of Feces
Chronic diarrhea defined as a passage of three or more liquid or loose stools in a day lasting for more than four weeks. Acute diarrhea refers to the passing of three or more liquid or loose stools in a day for less than four weeks. In diarrhea, stool examination is very important part of laboratory investigations. Depending on the nature of the investigation, either a random stool sample or 72- sample or 48-hour sample is collected. A random stool sample is used for the tests of occult blood, pH, fat, white blood cells, microscopy, or culture. A 72- or 48-hour sample is collected and examined for the weight, carbohydrate, fat content, osmolality, or chymotrypsin activity. Causes of chronic and acute diarrhea are listed in Table 988.1 and Figure 988.1 respectively.
1. Watery diarrhea
2. Inflammatory diarrhea
3. Fatty diarrhea
In infants and young children, Rotavirus is the most common cause of diarrhea. Rotavirus can be identified by the electron microscopic examination of stool. Other techniques, such as latex agglutination, immunofluorescence, or enzyme-linked immunosorbent assay (ELISA) are also used for the detection of Rotavirus in stool.
Chemical tests can be applied on feces to detect excess fat excretion (malabsorption syndrome), occult blood (in ulcerated lesions of the gastrointestinal tract, especially occult carcinoma of the colon) and presence or absence of urobilinogen (obstructive jaundice). See also: Chemical Examination of Feces
Feces is examined for the presence of white blood cells. Increased numbers of polymorphonuclear neutrophils (identified by methylene blue stain from the presence of granules in their cytoplasm) are seen as shown in Figure 988.2. See also: Causes, symptoms, diagnosis, and treatment of Cholera
Venous blood sample is collected from antecubital fossa in a test tube containing trisodium citrate (3.2%), with the anticoagulant to blood proportion being 1:9. See also: Prothrombin time (PT): Collection of Specimen.
Plasma is incubated with an activator (which initiates intrinsic pathway of coagulation by contact activation). Phospholipid (also called as partial thromboplastin) and calcium are then added and clotting time is measured.
It is one stage test. It distinguishes the functionality of the clotting factors I, II, V, VIII, X, XI, and XII. Both Activated Partial Thromboplastin Time (APTT) and Partial Thromboplastin Time (PTT) have the same clinical significance but Activated Partial Thromboplastin Time (APTT) is more reliable as compare to Partial Thromboplastin Time (PTT) due to its sensitivity.
Tissue thromboplastin and calcium are added to plasma and clotting time is determined. The test determines the overall efficiency of extrinsic and common pathways.
International Sensitivity Index (ISI) of a particular tissue thromboplastin is derived (by its manufacturer) by comparing it with a reference thromboplastin of known ISI. For standardization and to obtain comparable results, it is recommended to report PT (in persons on oral anticoagulants) in the form of an International Normalized Ratio (INR).
International Normalized Ratio (INR) is calculated by the following formula.
Purpose of INR: The INR is calculated to evaluate the following conditions.
Technique of APTT, PTT, and PT is different in different laboratories therefore normal values varies with the lab to lab. A normal control is always run with the patient's sample. In general, normal values are below.
|Disease||Required INR Value|
|Deep vein thrombosis prophylaxis||1.5 to 2.0|
|Deep vein thrombosis||2.0 to 3.0|
|Atrial fibrillation||2.0 to 3.0|
|Orthopedic surgery||2.0 to 3.0|
|Pulmonary embolism||2.5 to 3.5|
|Prosthetic valve prophylaxis||3.0 to 4.0|
For the estimation of Adrenocorticotropic hormone (ACTH), patient’s plasma is needed. Blood is collected in a chilled plastic test tube containing EDTA or heparin and blood is placed in cold ice-water.
The sample is centrifuged at 4º C, plasma is separated and stored at -20º C immediately within 15 minutes of the blood collection.
Note: For the diagnosis of Cushing Syndrome, the blood sample is collected in between 6 PM to 11 PM.
|Disease||ACTH Value||Cortisol Value|
|Ectopic ACTH (Lung cancer)||Raised||Raised|
|ACTH- producing Pituitary tumor||Raised||Raised|
|Adrenal gland failure ( Infarction, Haemorrhage)||Raised||Low|
|Congenital adrenal hyperplasia||Raised||Low|