Spanish health authorities said on Thursday they were investigating a possible outbreak of Crimean-Congo hemorrhagic fever (CCHF) which has killed one man and infected a nurse, in the first non-imported case reported in Western Europe.

The 62-year-old man died on Aug. 25 after contracting the CCHF disease during a walk in the Castilla-Leon region, probably from a tick bite he reported - which is one of the main ways it is transmitted - authorities said in a statement.

He also infected the nurse who treated him at a hospital in Madrid and she is now in a stable condition in quarantine at an isolation unit, they said. Authorities are monitoring about 200 other people who had come into contact with the man and nurse.

According to the World Health Organization, CCHF's mortality rate is about 30 percent and it is endemic to Africa, the Balkans and Ukraine, the Middle East and Central Asia.

Read more: First Local Case of Tick-Borne Disease Kills Man in Spain

When Blood is mixed with a solution of potassium cyanide, potassium ferricyanide, and Drabkin’s solution, the erythrocytes are lysed by producing evenly disturbed hemoglobin solution. Potassium ferricyanide transforms hemoglobin into methemoglobin, and methemoglobin combines with potassium cyanide to produce hemiglobincyanide (cyanmethemoglobin). This method is optional for estimation of hemoglobin and this method is recommended by the International Committee for Standardization in hemotology. This is because in this method all type of hemoglobin is transformed to cyanmethemoglobin (except sulfhemoglobin), and a firm and trustworthy standard is available.

An affordable, widely available test can impact today`s biggest healthcare challenge.

Description: You’re definitely aware of Thrombosis, the cloting of blood inside blood vessels and that its consequences can be in some cases dramatic.
 
For this reason you might be taking blood thinners (anti-clotting drugs or anticoagulants) which help you remedy this problem. With this treatment, some standards and coefficients are required to monitor the coagulation levels of your blood during treatment stages.
 
The INR or International Normalized Ratio was developed to report the results of clotting tests. At the time it was implemented, the main purpose was to standardize PT (prothrombin time) because the test results were inconsistent, varying from one lab to the other.
 
To determine your INR ratio in a simple manner, INR Calculator is designed. With it you can calculate the ratio in a few simple steps. All that is required is for you to enter the values for the ‘PT patient’ , ‘PT normal’ and ‘ISI’ then simply click ‘Calculate’. The resulting number is immediately displayed with all its decimals.
 
INR Calculator is very easy to install and use. It’s a browser based application that requires almost no system resources to run which makes it a good solution for on the fly situations.
 
It does indeed help you out when you don’t have another quick way of obtaining the INR value but in order to be able to use it correctly, you need to know all the other values which apply to your case. The PT and ISI ( International sensitivity index) need to be accurate.
 
In closing, INR Calculator is a handy and practical application that can definitely prove helpful when you want to obtain your INR value.
 
Useful Links:

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  • Year 2016
  • Author(s) Dayyal Dg.
  • Publisher BioScience.pk
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When blood is mixed with an acid solution, the hemoglobin converts into the brown-colored acid hematin. The acid hematin is then diluted with distilled water till the color of the acid hematin matches that of the brown glass standard. The hemoglobin is estimated by reading the value directly from the scale.

Description: Now in a thoroughly revised and updated Sixth Edition, Localization in Clinical Neurology is cornerstone in clinical neurology.  Designed to aid clinicians in their quest to locate the source of commonly encountered neurologic disorders, the text provides detailed descriptions and clear illustrations to help improve diagnostic accuracy and avoid unnecessary testing. Organization by anatomic and brain region makes vital information easy to find and use.
 
NEW to the Sixth Edition…
 
• Nearly 100 color illustrations provide the clear anatomic information needed to refine clinical diagnosis.
• Comprehensive coverage addresses all brain regions, as well as cranial, spinal, and peripheral nerves.
• Detailed discussions address relevant anatomy, followed by a discussion of lesions related to each anatomic feature.
• A new chapter addresses the localization of lesions of the autonomic nervous system.
 
 An outstanding roadmap to neurologic diagnosis!

Additional Info

  • File Name Localization in Clinical Neurology, 6th Ed.
  • Edition 6th
  • Year 2011
  • Author(s) Paul W. Brazis MD, Joseph C. Masdeu MD PhD, José Biller MD FACP FAAN FAHA
  • ISBN-10 1609132815
  • ISBN-13 978-1609132811
  • Publisher LWW; Sixth edition (March 29, 2011)
  • Size 20 MB
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HEMOGLOBIN

Hemoglobin is composed of heme (iron + protoporphyrin) and globin polypeptide chains. It is present in the red blood cells of all vertebrates except Channichthyidae (the family of fish: white-blooded fish also called crocodile fish found in southern South America and the Southern Ocean around Antarctica). It carries oxygen from the lungs to the tissues and carbon dioxide from tissues to the lungs.

In humans, hemoglobin is not homogeneous and normally different variants and derivatives exist. Normal hemoglobin variants are fetal hemoglobin (Hb F), adult hemoglobin (Hb A), Hb A2 and embryonic hemoglobins (Gower I, Gower II and Portland). They differ from each other on the basis of the structure and the type of polypeptide chains.

INDICATION FOR HEMOGLOBIN ESTIMATION

  1. Screening for polycythemia: Polycythemia is a disease state in which the hemoglobin level and hematocrit (HCT) or packed cell volume (PCV) value is elevated. It may be primary, secondary or relative.
  2. To determine presence and severity of anemia: Anemia is a disease state in which the hemoglobin concentration or oxygen-carrying capacity of blood is low. Clinical signs and symptoms (conjunctival vessels, polar of skin, mucosal membranes) are unreliable for the diagnosis of anemia. Anemia is best determined by estimation of hemoglobin and hematocrit (HCT) or packed cell volume (PCV).
  3. To assess response to specific therapy in anemia.
  4. Estimation of red cell indices (along with hematocrit (HCT) or packed cell volume (PCV) and red cell count) i.e. mean cell volume (MCV), mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC).
  5. Selection of blood donors in the blood bank.

METHOD FOR ESTIMATION OF HEMOGLOBIN

There are different methods for estimation of hemoglobin. These are:

(1) Colorimetric methods: In these methods, the color comparison is made between the standard and the test sample, either visually or by colorimetric methods.

(2) Gasometric method: In this method, oxygen-carrying capacity of red blood cells (RBCs) is measured in a Van Slyke apparatus. The amount of hemoglobin is then derived from the formula that 1 gram of hemoglobin carries 1.34 ml of oxygen. However, this method measures only physiologically active hemoglobin, which can carry oxygen. It does not measure methemoglobin, sulfhemoglobin, and carboxyhemoglobin. Also, this method is expensive and time-consuming, and the result is about 2% less than other methods.

(3) Chemical method: In this method, iron-content of hemoglobin is first evaluated. The value of hemoglobin is then derived indirectly from the formula that 100 grams of hemoglobin contain 374 mg of iron. This method is tiresome and time-consuming.

(4) Specific gravity method: In this method, an approximate value of hemoglobin is estimated from the specific gravity of blood as determined from copper sulfate technique. This method is simple and rapid. This method is useful and most common in mass screening like the selection of blood donors. See procedure.

Tallqvist Hemoglobin Chart

Tallqvist hemoglobin chart consists of a series of lithographed colors said to correspond to hemoglobin values ranging from 10% to 100%. In this method, a drop of blood obtained by finger puncture is placed on a piece of absorbent paper. The color produced is matched against the color on the chart and the corresponding reading is taken. The room of error is 20-50%. Although this method is very cheap and simple.

Red Cell Indices

Red cell indices are mean cell volume (MCV), mean cell hemoglobin (MCH), and mean cell hemoglobin concentration (MCHC). They are also called as “absolute values”. They are derived from the values of hemoglobin, packed cell volume (PCV or hematocrit), and red cell count. Red cell indices are accurately measured by automated hematology analyzers. Recently, a new parameter called red cell distribution width (RDW) has been introduced.
 
USES OF RED CELL INDICES
 
(1) Morphological classification of anemia: Based on values of red cell indices, anemia is classified into three main types: normocytic normochromic, microcytic hypo-chromic, and macrocytic normo-chromic. Calculation of red cell indices is especially helpful in mild or moderate anemia when red cell changes are subtle and often difficult to appreciate on stained blood smear.
(2) Differentiation of iron deficiency anemia from thalassemia trait: In iron deficiency, MCV, MCH, and MCHC are low, while in thalassemia trait, MCV and MCH are low and MCHC is normal.
 
MEAN CELL VOLUME
 
MCV is a measure of average size of the red cells. It is measured directly by automated instruments from the measurement of volume of each red cell. With semiautomated instruments and by manual method, it is obtained by dividing PCV by red cell count.
 
MCV =                PCV in%                  x 10
            RBC count in million/cmm
 
     MCV is expressed in femtoliters or fl (10⁻¹⁵ of a liter). It corresponds with red cell diameter on blood smear. Normal MCV is 80-100 fl.
 
Causes of Increased MCV
 
• Megaloblastic anemia
• Non-megaloblastic macrocytosis: Chronic alcoholism, liver disease, hypothyroidism, normal pregnancy, reticulocytosis
• Newborns.
 
Causes of Low MCV
 
• Microcytic hypochromic anemia
 
MCV is normal in normocytic normochromic anemia (acute blood loss, hemolysis, aplastic anemia).
     In the presence of large number of abnormal red cells like sickle cells, and in dimorphic anemia (e.g. mixed normocytic and microcytic), MCV may be normal (since it is an average value) and thus unreliable for morphological classification.
     Mentzer index is derived by dividing MCV with red cell count. Ratio of less than 13 is seen in thalassemia while ratio is more than 13 in iron deficiency anemia.
 
MEAN CELL HEMOGLOBIN (MCH)
 
MCH is the average amount of hemoglobin in a single red cell. It is obtained by dividing hemoglobin value by red cell count.
 
MCH =    Hemoglobin in grams/dl     x 10
           RBC count in millions/cmm
 
MCH is expressed in picograms or pg (10⁻¹² gram). Reference range is 27-32 pg.
     MCH is decreased in microcytic hypochromic anemia, and increased in macrocytic anemia and in newborns.
 
MEAN CELL HEMOGLOBIN CONCENTRATION (MCHC)
 
MCHC is obtained by dividing hemoglobin value by PCV and expressed in grams/dl or grams/liter. It refers to concentration of hemoglobin in 1 dl or 1 liter of packed red cells.
 
MCHC = Hemoglobin in grams/dl  x 100
                        PCV in %
 
Reference range is 30-35 grams/dl. MCHC is raised in hereditary spherocytosis, and is decreased in hypochromic anemia. MCHC corresponds with degree of hemoglobinization of red cells on a blood smear. If MCHC is normal, red cell is normochromic, and if low, red cell is hypochromic.
 
Red Cell Distribution Width (RDW)
 
Some automated analyzers measure red cell distribution width or RDW. It is a measure of degree of variation in red cell size (anisocytosis) in a blood sample. It is helpful in differential diagnosis of some anemias. Amongst microcytic anemias, RDW is low in ß thalassemia trait, high in iron deficiency anemia, and normal in anemia of chronic disease. Normal RDW is 9.0 to 14.5.
 
REFERENCE RANGES
 
• Mean cell volume: 80-100 fl
• Mean cell hemoglobin: 27-32 pg
• Mean cell hemoglobin concentra-tion: 30-35 g/dl
• Red cell distribution width: 9.0-14.5
 
REFERENCES
 
1. Henry JB. Clinical diagnosis and management by laboratory methods (20th Ed). Philadelphia: WB Saunders Company, 2001.
2. Wallach J. Interpretation of Diagnostic Tests (7th Ed). Philadelphia: Lippincott Williams and Wilkins, 2000¹⁵

Abdominal and pelvic masses manifest as swellings in specific areas of the abdomen and pelvis. They are often incidentally picked up on physical examination. Most causes of abdominal masses are benign, but some might indicate a serious underlying pathology.

This video will provide a comprehensive diagnostic approach to a patient with an abdominal/pelvic mass. Critical questions to ask in history, such as intercurrent symptoms of change in bowel habit or urinary difficulties, and important features on physical examination, such as reducible masses and midline pulsatile masses, will be reviewed. Laboratory and imaging investigations, while not absolutely necessary, can be ordered and the significance of findings on these will also be discussed. Lastly, you will learn about the management of some serious causes of abdominal masses, such as abdominal aortic aneurysm and hernias.

Porphyrias

Porphyrias (from Greek porphura meaning purple pigment; the name is probably derived from purple discoloration of some body fluids during the attack) are a heterogeneous group of rare disorders resulting from disturbance in the heme biosynthetic pathway leading to the abnormal accumulations of red and purple pigments called as porphyrins in the body. Heme, a component of hemoglobin, is synthesized through various steps as shown in figure. Each of the steps is catalyzed by a separate enzyme; if any of these steps fails (due to hereditary or acquired cause), precursors of heme (porphyrin intermediates) accumulate in blood, get deposited in skin and other organs, and excreted in urine and feces. Depending on the site of defect, different types of porphyrias are described with varying clinical features, severity, and the nature of accumulated porphyrin.
 
Porphyria has been offered as a possible explanation for the medieval tales of vampires and werewolves; this is because of the number of similarities between the behavior of persons suffering from porphyria and the folklore (avoiding sunlight, mutilation of skin on exposure to sunlight, red teeth, psychiatric disturbance, and drinking of blood to obtain heme).
 
Porphyrias are often missed or wrongly diagnosed as many of them are not associated with definite physical findings, screening tests may yield false-negative results, diagnostic criteria are poorly defined and mild disorders produce an enzyme assay result within ‘normal’ range.
 
Heme is mainly required in bone marrow (for hemoglobin synthesis) and in liver (for cytochromes). Therefore, porphyrias are divided into erythropoietic and hepatic types, depending on the site of expression of disease. Hepatic porphyrias mainly affect the nervous system, while erythropoietic porphyrias primarily affect the skin. Porphyrias are also classified into acute and nonacute (or cutaneous) types depending on clinical presentation.
 
Inheritance of porphyrias may be autosomal dominant or recessive. Most acute porphyrias are inherited in an autosomal dominant manner (i.e. inheritance of one abnormal copy of gene). Therefore, the activity of the deficient enzyme is 50%. When the level of heme falls in the liver due to some cause, activity of ALA synthase is stimulated leading to increase in the levels of heme precursors up to the point of enzyme defect. Increased levels of heme precursors cause symptoms of acute porphyria. When the heme level returns back to normal, symptoms subside.
 
Accumulation of porphyrin precursors can occur in lead poisoning due to inhibition of enzyme aminolevulinic acid dehydratase in heme biosynthetic pathway. This can mimick acute intermittent porphyria.

“I can focus my slide under 10×, but not under 40×.”

A common reason for this is that the slide is upside down. Double check which side the smear is on (may not be the same side as the label!) and try focusing again. Another cause could be dried immersion oil on the 40× objective that is obstructing your view. When switching from oil immersion (100×) to 40×, there is a good chance that the tip of the 40× objective could be dragged through some immersion oil. If it is not immediately cleaned off, it will dry, producing a thick haze. To fx: Use lens paper and lens cleaner to clean the end of the 40× objective. This may need to be repeated several times depending on how thick the dried oil is. After cleaning, use a dry piece of lens paper to polish the objective. To avoid the problem: Clean up oil immediately after use. Clean the end of the 100× objective and any heavy oil present on the slide before moving back down to 40× objective.

“In hematology, when I focus under 40×, my red blood cells appear shiny.”

This is most likely due to water artifact during the staining and drying process. To make visualization of the cells easier, add a small drop of immersion oil to your slide. Gently spread the drop of oil over the area you will be examining. Wipe of excess oil using the side of your finger. Be very gentle when doing this, and use a clean finger each time you wipe. Wiping too hard or rough will cause your smear to rub off. This technique will leave a very thin layer of oil on your smear. The film is thin enough that you can use the 40× objective without running the risk of the lens becoming contaminated with oil. Try focusing under 40× again, and the shininess should have been resolved.

“There’s no light coming from the illuminator.”

The first assumption is always that the bulb is burnt out, but it is a good idea to check a couple of other possibilities as well. If the iris diaphragm is closed and the brightness of the illuminator is at its lowest, the light may be so small that it appears as if there is no light present. Check to make sure the cord is fully plugged into the back of the microscope. This plug can become dislodged slightly during transport and microscope set up. If your microscope is the type that uses fuses, it may be the fuse—not the bulb—that needs replacing. When the microscope is not in use, be sure to turn it off. This will help prolong the life of the bulb.

Clean up

When the use of the microscope is complete, following proper clean up procedures will improve the quality of images that are viewed and extend the life of the microscope and its components:

  1. Remove the slide from the stage and dispose of it properly.
  2. Clean any oil residue or sample material that may have contaminated the stage surface.
  3. Lower the stage and move the smallest objective into place.
  4. Clean the objective lens and oculars after every use. The order in which they are cleaned is important. Cleaning the 100× objective first and then moving onto other parts will result in immersion oil being spread onto all other components. Using lens tissue and lens cleaner, begin with cleaning the oculars, then the 4× objective, the 10× objective, 40× objective, and finish with the 100× objective lens.
Single Best Answers in Surgery offers a new approach to revising for surgical finals; by not only indicating the correct answer to each question, but explaining the full rationale used for finding the answer in each case. This means the book is invaluable not only for self-testing before an exam, but will have long-term value throughout a student's surgical studies, through to finals exams and beyond. The questions are arranged into topic areas, followed by a practice exam for true self-assessment.
 
Single Best Answers in Surgery contains 450 questions and answers in the following areas:
 
(1) Pre- and Postoperative Management, (2) Fluid Balance and Parenteral Nutrition, (3) Trauma, (4) Abdomen: Upper GI and Hepatobiliary Surgery, (5) Abdomen: Lower GI Surgery (6) Abdomen: The Acute Abdomen, (7) Breast Surgery, (8) Vascular Surgery, (9) Urology, (10) Orthopaedics, (11) Neurosurgery, (12) ENT Surgery, (13) Ophthalmic Surgery, (14) Lumps, Bumps, Skin and Hernias, (15) Practice exam
 
Produced by an excellent team of authors and with an introduction by Editorial Advisor Professor Sir Ara Darzi KBE.

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  • File Name Single Best Answers in Surgery
  • Edition 2nd
  • Year 2009
  • Author(s) Darren K Patten, David Layfield, Shobhit Arya, Daniel R Leff, Paraskevas A. Paraskeva
  • Editor(s) Professor Sir Ara Darzi
  • ISBN-10 0340972351
  • ISBN-13 978-0340972359
  • Publisher CRC Press; 1 edition (27 Mar. 2009)
  • Size 4.26 MB
  • File Format .pdf
  • Password bioscience.pk
About the Author

Dennis Kasper, MD is Professor of Medicine at Harvard and a leading researcher of the health and disease implications related to host-microbe interactions and the human microbiome.
Anthony Fauci, MD is Director of the National Institutes for Allergy and Infectious Diseases, and recipient of the Lasker Prize for Medicine. He is a leading authority in HIV and AIDS, immunology, and management of Ebola Virus Disease.
Dan Longo, MD is Deputy Editor, New England Journal of Medicine and Professor of Medicine, Brigham and Women's Hospital/Harvard Medical School. Dr. Longo is a highly regarded cancer specialist.
Stephen Hauser MD is Robert A. Fishman Distinguished Professor and Chair, Department of Neurology, UCSF School of Medicine. He is a leading authority on multiple sclerosis.
J. Larry Jameson, MD, PhD is Robert G. Dunlop Professor of Medicine, Dean, University of Pennsylvania School of Medicine, and Executive Vice President, University of Pennsylvania Health System.
Joseph Loscalzo MD, PhD is Hersey Professor of the Theory and Practice of Medicine, Harvard Medicine School and a leading authority in many aspects of cardiovascular medicine.

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  • File Name Harrison's Principles of Internal Medicine, 19th Ed.
  • Edition 19th
  • Year 2015
  • Editor(s) Dennis Kasper, Anthony Fauci, Stephen Hauser, Dan Longo, J. Larry Jameson, Joseph Loscalzo
  • ISBN-10 0071802150
  • ISBN-13 978-0071802154
  • Publisher McGraw-Hill Education / Medical; 19 edition (April 8, 2015)
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Since its inception in 1963, the National Institute of Cardiovascular Diseases (NICVD) has played a pivotal role in caring for patients with heart disease in Pakistan. NICVD is the first tertiary cardiac care institute in South Asia as well as the flagship facility for cardiology in Pakistan with a focus on superior care for patients, education and training for medical professionals, and research and development in cardiology.
 
NICVD caters to the cardiovascular needs of a vast majority of patients from all provinces of Pakistan as well as Afghan refugees and patients from other neighboring countries. It is responsible for training the bulk of local cardiac physicians, nurses and paramedics throughout the country.

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  • File Name NICVD Test Paper for Lab Technician Job Opportunity - June 2015
  • Year 2015
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When the recipient’s ABO and Rh blood groups are determined, the donor blood unit that is ABO and Rh compatible is selected, and compatibility test is carried out. The purpose of compatibility test is to prevent the transfusion of incompatible red cell units and thus avoidance of hemolytic transfusion reaction in the recipient. Compatibility test detects (i) major ABO grouping error, and (ii) most clinically significant antibodies reactive against donor red cells.

There are two types of cross-match: major cross-match (testing recipient’s serum against donor’s red cells) and minor cross-match (testing donor’s serum against recipient’s red cells). However, minor cross-match is considered as less important since antibodies in donor blood unit get diluted or neutralized in recipient’s plasma. Also, if antibody screening and identification is being carried out, minor cross-matching is not essential. Therefore, only the red cells from the donor unit are tested against the recipient’s serum and the name compatibility test has replaced the term cross-matching. For transfusion of platelets or fresh frozen plasma, cross-matching is not required. However, fresh frozen plasma should be ABO-compatible.

A full cross-matching procedure consists of:

  • Immediate spin cross-match at room temperature, and
  • Indirect antiglobulin test at 37°C.

IMMEDIATE SPIN CROSS MATCH

The purpose of this test is to detect ABO incompatibility. Equal volumes of 2% saline suspension of red cells of donor and recipient’s serum are mixed, incubated at room temperature for 5 minutes, and centrifuged. Agglutination or hemolysis indicates incompatibility.

Causes of False-negative Test

  1. A2B donor red cells and group B recipient serum.
  2. Rapid complement fixation of potent ABO antibodies with bound complement interfering with agglutination.

Causes of False-positive Test

  1. Rouleaux formation
  2. Cold-reactive antibodies: If agglutination disappears by keeping the tube at 37°C for 10 minutes, presence of cold agglutinins is confirmed.

INDIRECT ANTIGLOBULIN TEST

Saline-suspended red cells of the donor after being incubated in patient’s serum are washed in saline and antiglobulin reagent is added. Following re-centrifugation, examine for agglutination or hemolysis. This test detects most of the clinically significant IgG antibodies.

If agglutination or hemolysis is not observed in any of the above stages, donor unit is compatible with recipient’s serum. Agglutination or hemolysis at any stage is indicative of incompatibility.

EMERGENCY CROSS-MATCH

If blood is required urgently, ABO and Rh grouping are carried out by rapid slide test and immediate spin cross match (i.e. the first stage of cross match) is performed (to exclude ABO incompatibility). If the blood unit is compatible, then after issuing it, remaining stage of the cross-match is completed. If any incompatibility is detected, the concerned physician is immediately informed about the incompatibility detected.

ANTIBODY SCREENING AND IDENTIFICATION

Screening for unexpected or irregular antibodies is done during pre-transfusion testing in recipient’s serum and in donor’s blood. In this test, serum of the recipient is tested against a set of three group O screening cells of known antigenic type. If unexpected antibodies are detected, then they are identified and blood unit that lacks the corresponding antigen is selected for compatibility test.

ABSTRACT

The current paradigm in vaccine development is that nonreplicating vaccines delivered parenterally fail to induce immune responses in mucosal tissues. However, both clinical and experimental data have challenged this concept, and numerous studies have shown that induction of mucosal immune responses after parenteral vaccination is not a rare occurrence and might, in fact, significantly contribute to the protection against mucosal infections afforded by parenteral vaccines. While the mechanisms underlying this phenomenon are not well understood, the realization that parenteral vaccination can be an effective means of inducing protective mucosal responses is paradigm-shifting and has potential to transform the way vaccines are designed and delivered.
 

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  • File Name Parenteral Vaccination Can Be an Effective Means of Inducing Protective Mucosal Responses
  • Year 2016
  • Author(s) John D. Clements and Lucy C. Freytag
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  • Preview http://cvi.asm.org/content/23/6/438.full
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APTT is a measure of coagulation factors in intrinsic pathway (F XII, F XI, high molecular weight kininogen, prekallikrein, F IX, and F VIII) and common pathway (F X, F V, prothrombin, and fibrinogen).
 
Principle
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.
 
Equipment
This is same as for Prothrombin Time test. (Click here to see)
 
Reagents
(1) Kaolin 5 gm/liter: This is a contact activator.
(2) Phospholipid: Various APTT reagents are available commercially, which contain phospholipids.
(3) Calcium chloride 0.025 mol/liter.
 
Specimen
Method
(1) Mix equal volumes of phospholipid reagent and calcium chloride solution in a glass test tube and keep in a waterbath at 37°C.
(2) Deliver 0.1 ml of plasma in another test tube and add 0.1 ml of kaolin solution. Incubate at 37°C in the waterbath for 10 minutes.
(3) After exactly 10 minutes, add 0.2 ml of phospholipidcalcium chloride mixture, start the stopwatch, and note the clotting time.
 
Normal Range
30-40 seconds.
 
Causes of prolongation of APTT
(1) Hemophilia A or B.
(2) Deficiencies of other coagulation factors in intrinsic and common pathways.
(3) Presence of coagulation inhibitors
(4) Heparin therapy
(5) Disseminated intravascular coagulation
(6) Liver disease
 
Uses of APTT
(1) Screening for hereditary disorders of coagulation: Since deficiencies of F VIII (hemophilia A) and F IX (hemophilia B) are relatively common, APTT is the most important screening test for inherited coagulation disorders. APTT detects deficiencies of all coagulation factors except F VII and F XIII. PT is also performed along with APTT. Prolongation of both PT and APTT is indicative of deficiency of coagulation factors in common pathway. Normal PT with prolongation of APTT is indicative of intrinsic pathway deficiency (particularly of F VIII or IX).
(2) To monitor heparin therapy: Heparin potentiates the action of natural anticoagulant antithrombin III which is an inhibitor of thrombin and activated factors IX, X, and XI. Full dose heparin therapy needs monitoring by APTT to maintain the dose in the therapeutic range (1.5 to 2.5 times the upper reference limit of APTT).
(3) Screening for circulating inhibitors of coagulation: APTT is prolonged in the presence of specific inhibitors (which are directed against specific coagulation factors) and non-specific inhibitors (which interfere with certain coagulation reactions).
 
Mixing experiment for detection of inhibitors: Mixing studies are used to distinguish between factor deficiencies and factor inhibitors (specific coagulation factor inhibitor or non-specific inhibitor such as lupus anticoagulant). If APTT is prolonged, patient’s plasma is mixed with an equal volume of normal plasma (called as a 50:50 mix) and APTT is repeated. In coagulation factor deficiency, prolongation of APTT gets corrected by more than 50% of the difference between the clotting times of control and test plasma. In the presence of lupus anticoagulant, there is no such correction. With lupus anticoagulant, APTT remains prolonged after mixing and for 2 hours following incubation. With F VIII inhibitor (which is time- and temperature-dependent), prolong-ed APTT gets immediately corrected after mixing, but becomes prolonged after incubation.