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Sunday, December 21, 2014

Why Cardiac Troponin Test need to be Repeated Several Times in a case of Suspected Acute Coronary Syndrome (ACS)

Posted by Prahallad Panda on 7:08 PM Comments


Importance:
Cardiac Troponin (cTn) I or T need to be repeated at least once after 12 hours of onset of the symptoms, if patient is seen within 12 hours and the initial result is negative to exclude the diagnosis of Myocardial Infarction. Highly sensitive cTn may be repeated 2-3 hourly for two to three times for the same purpose.
Normal Values 1
Cardiac troponin levels are normally so low they cannot be detected with most blood tests. Troponins are found only in skeletal muscles and heart muscles; smooth muscle cells do not contain troponins.
Test results are usually considered normal if the results are:
  • Troponin I : less than 10 µg/L
  • Troponin T : 0–0.1 µg/L
Normal troponin levels after 12 hours of chest pain mean a heart attack is unlikely.
What abnormal results mean:
An increase in the troponin level, even a slight one, usually means there has been some damage to the heart. Significantly high levels of troponin are a sign that a heart attack has occurred.
Most patients who have had a heart attack have increased troponin levels within 6 hours. After 12 hours almost everyone who has had a heart attack will have raised levels.
Troponin levels may remain high for 1 to 2 weeks after a heart attack.
Increased troponin levels may also be due to:
  • Abnormally fast heart beat
  • High blood pressure in lung arteries (pulmonary hypertension)
  • Blockage of a lung artery by a blood clot, fat, or tumor cells (pulmonary embolus)
  • Congestive heart failure
  • Coronary artery spasm
  • Inflammation of the heart muscle usually due to a virus (myocarditis)
  • Strenuous exercise (for example, due to marathons or triathlons)
  • Trauma that injures the heart such as a car accident
  • Weakening of the heart muscle (cardiomyopathy)
Increased troponin levels may also result from certain medical procedures such as:
  • Cardiac angioplasty/stenting
  • Heart defibrillation or electrical cardioversion (purposeful shocking of the heart by medical personnel)
  • Open heart surgery
  • Radiofrequency ablation of the heart
The Changing Scenario:
Previously, clinicians often had to wait an average of 6 hours with the lower-sensitivity, lower-precision cTn assays to see a conclusive increase in plasma cTn levels after the first troponin measurement, but today's high-sensitivity cTn tests that are separated by a mere 2 to 3 hours, can be highly informative.
Given the urgent need for early diagnosis of ACS and appropriate emergency intervention, as well as the ease of performing this relatively inexpensive assay, clinicians do not need to wait 6 to 8 hours before ordering a second troponin test to rule in ACS.
It is recommend to collect a second specimen for cTn testing within 2 to 3 hours from the collection of the blood sample at presentation to help confirm the diagnosis of MI.
Why dynamics of Troponin is Important:
The most common cause of cardiac injury is myocardial ischemia, ie, acute myocardial infarction. To be detectable, Troponin T takes 2 to 4 hours after the onset of myocardial necrosis, attends peak after about 12 hours and can remain elevated for up to 14 days.
In patients with MI, there is a lag before troponin elevations can be detected.Thus, the markers should be serially monitored upon suspicion for acute coronary syndrome (ACS). The initial recommendations were to check the markers every 6 hours until the expected peak was reached. However, with the more sensitive assays now available, very low concentrations of elevated cardiac markers can be detected, and evidence has demonstrated that checking troponins 3-4 hours after the initial draw can help in early diagnosis of ACS.
The safest rule of thumb is that a single negative test result for troponin does not exclude AMI in a patient with current or very recent symptoms, nor does it exclude clinically significant coronary artery disease.
Let us go here to recapitulate the physiological Role of Troponin in cardiac muscle contraction to appreciate it

 
Importance of the Dynamics of Troponin:
The dynamics of troponin levels (rise and/or fall over time) help distinguish AMI from non-AMI conditions, thus serial troponin testing is the standard approach recommended for assessing patients with suspected acute coronary syndrome (ACS).
The safest rule of thumb is that a single negative test result for troponin does not exclude AMI in a patient with current or very recent symptoms, nor does it exclude clinically significant coronary artery disease.
About acute myocardial infarction (AMI)
  1. AMI is part of a group of conditions collectively known as acute coronary syndrome (ACS), which includes both ST-segment-elevation myocardial infarction (STEMI) and non-ST-segment-elevation myocardial infarction (NSTEMI), and unstable angina.
  2. These conditions are associated with common symptoms but have different underlying pathologies; STEMI is usually associated with a relatively large amount of damage (Transmural) to the myocardium (heart muscle) caused by a major blockage in the coronary artery, and can be detected with ST-elevation on an ECG trace. By comparison, NSTEMI is associated with relatively less damage to myocardium (Sub-endocardial) caused by partial blockage of the coronary artery or blockage of a smaller artery, and does not produce ST-elevation on ECG.
  3. Acute coronary syndromes arise from an obstruction in the coronary arteries, usually caused by atherosclerosis and build-up of plaque which ruptures. When blood flow to the heart is reduced or blocked for a significant length of time (around 30-60 minutes) damage to cardiomyocytes (heart muscle cells) occurs, a pathological change which distinguishes an AMI from unstable angina.
  4. Patients with ACS generally present with chest pain, a symptom which is responsible for around 700,000 emergency department attendances per year in England and Wales and 253,765 emergency admissions per year.
  5. During 2011/12, the Myocardial Ischaemia National Audit Project (MINAP) reported 79,433 admissions with AMI recorded in England and Wales, 32,439 (41%) of which were categorised as STEMI, and 46,994 (59%) were categorised as NSTEMI.
  6. The incidence of acute myocardial infarction increases with age, with the average age of first STEMI being 65 years, and of first NSTEMI 70 years. The incidence is also greater amongst men, with men being twice as likely to have an AMI as women.

Why Troponin test is preferred to Creatine Kinase MB

The skeletal and cardiac muscle troponin T and troponin I are immunologically distinct entities. Separate sets of genes code for these proteins. Thus, the cardiac troponin assays, which rely on antigen antibody interaction, are specific for cardiac troponins and can be used to differentiate between the skeletal and cardiac troponins.
Cardiac troponin levels do not rise in the presence of skeletal damage without cardiac myocyte damage. However, this is not the case for creatine kinase MB, which, being present to some extent in skeletal muscle and several other tissues such as the intestines, tongue, diaphragm, uterus, and prostate, may be elevated upon injury to these tissues, potentially resulting in false-positive results. Because of this, troponin testing is superior to creatine kinase MB testing.
Status of Electrocardiography (ECG) as a single mode of diagnosis of AMI:
Electrocardiography (ECG) was one of the earliest diagnostic modalities introduced to evaluate ischemic injury to the heart. Despite its usefulness, ECG continues to be nonsensitive in diagnosing ischemic cardiac events, as ECG findings are normal in many patients with ischemic injury.
The introduction of various markers of cardiac injury, such as creatinine kinase MB, troponins, and myoglobins, has revolutionized the diagnosis of myocardial injury. The cardiac troponins, by virtue of being the most sensitive and specific, have become the preferred biomarker for evaluation of patients with suspected MI.

Determining infarct size:
Peak troponin values can provide an estimate of the infarct size and the severity of myocardial damage. These values are more sensitive in the setting of transmural infarction (ST-segment–elevation MI [STEMI]) than in subendocardial infarctions (NSTEMI). This correlation holds true for both troponin T and troponin I (peak or values at 72-96 hours). Higher values generally correlate with a larger infarct
Significance of degree of troponin elevation
The degree of troponin elevation correlates well with both the 30-day mortality and long-term mortality. Various clinical trials have evaluated the degree of elevation of both troponin I and troponin T and found that higher elevations at presentation and peak are associated with worse long-term outcomes. The absolute values have been used to guide treatment decisions and to identify patients who are at an increased risk of death.
Prognostic value of the timing of elevation
Patients who present with elevated troponin levels at baseline tend to have worse outcomes than those in whom troponin levels are elevated at 8 hours. Outcomes are best in patients in whom troponin levels never elevate.
In both STEMI and NSTEMI, elevated levels of troponin T and troponin I at presentation are associated with a worse prognosis in terms of both short-term and long-term mortality. 
 
How often to perform troponin testing and the need for serial testing


In patients with MI, there is a lag before troponin elevations can be detected.Thus, the markers should be serially monitored upon suspicion for acute coronary syndrome (ACS). The initial recommendations were to check the markers every 6 hours until the expected peak was reached. However, with the more sensitive assays now available, very low concentrations of elevated cardiac markers can be detected, and evidence has demonstrated that checking troponins 3-4 hours after the initial draw can help in early diagnosis of ACS.





Reference:
http://emedicine.medscape.com/article/2073935-overview#a30
Jaffe AS: 2001-A biomarker odyssey. Clin Chim Acta 1999;284:197-211


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Sunday, November 2, 2014

Role of CT Abdomen in Pyrexia of Unknown Origin to Differentiate between Lymphoma and Tuberculosis

Posted by Prahallad Panda on 7:34 PM Comments


Fever of unknown origin (FUO) was defined in 1961 as:
  1. A temperature greater than 38.3°C (101°F) on several occasions,
  2. More than 3 weeks' duration of illness, and
  3. Failure to reach a diagnosis despite 1 week of inpatient investigation.
Now, most of diseases that may cause continuous fever and dilemma in arriving at diagnosis decreased after the advent of various imaging and investigative technologies. 
The most common causes of FUO like tuberculosis, collagen diseases, AIDS and malignancies can be diagnosed by newer serological tests, ultrasonogram, CT, MRI and PET/CT etc..
In spite of all these, there may be occasions, where it may not be possible to differentiate mesenteric lymphadenopathay of lymphoma and tuberculous aetiology without any other associated features.

Intra-Abdominal Lymph Nodes
In multi-detection computerized tomography (MDCT), it has been seen that lymphadenopathy of tuberculous origin mostly affect the LN (Lymph node) adjacent to the intestinal mesenteric boarder, where as in lymphoma more distant LN like para-aortic are involved.
Tuberculosis predominantly involved lesser omental, mesenteric, and upper para-aortic lymph nodes whereas lower para-aortic lymph nodes were involved more often in Hodgkin’s and non-Hodgkin’s lymphoma.
Peripheral enhancement is most commonly seen in tuberculosis, whereas homogeneous enhancement is seen in lymphoma.
The contrast enhancement of tuberculous lymph nodes on contrast-enhanced CT (CECT) have been described as (four patterns) - peripheral rim enhancement, inhomogeneous enhancement, homogeneous enhancement and homogeneous non-enhancement, in that order of frequency.
'Sand-witch' sign, encasing of superior mesenteric vessels and fat (Filling) by the lymph node mass as “Bun” is most commonly seen in lymphoma.
In a study, the mean diameters were 2.95 cm in tuberculous lymphadenopathy, whereas it was 4.10 cm in lymphoma.
Associated findings like thickening of intestine, ascites and peritoneal thickening are more commonly seen in tuberculosis.
In spite of all, a CT/USG guided FNAC or laparoscopic tissue diagnosis is required for the final diagnosis and treatment planning.

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Thursday, October 2, 2014

Importance of Hand Washing & Hygiene in Preventing Infectious Diseases

Posted by Prahallad Panda on 9:01 AM Comments



As India is all set to observe “National Cleanliness Day” to-day i.e. 02.10.2014, on the birth anniversary of “father of Nation”; Mahatma Gandhi; I thought, it will be proper to put this article on Web as a small contribution towards the larger cause.
Do we remember Typhoid Mary? Mary Mallon, better known as Typhoid Mary, a Cook, who got this nick name after spreading Typhoid in about 50 people in New York City in the early 1900s without succumbing to the illness herself. This a bright example of faeco-oral route of transmission of disease.
Various infections are transmitted through hand. Health care persons and those handling food are important vectors. 
In addition, Elementary schoolchildren are important vectors for spreading infectious diseases between themselves and their families.
Infectious agents that children contract in schools can result in infections in up to 50% of household members.
100 trillion microbial symbionts (the human microbiota). Your body is home to 10 times as many microbes as its own cells. The human skin contains microbes that reside either in or on the skin and can be residential or transient. Swab samples from about 200 volunteers' belly buttons contained an astonishing variety of bacteria, nearly 4,000 different strains, many of which are completely new to scientists.
Infectious agents that children contract in schools can result in infections in up to 50% of household members.

The Facts behind the Urgency:

There are many types of germs (viruses, bacteria, parasites, fungi) that cause many types of illnesses– including the common cold or flu, food borne illness, Lyme disease, hantavirus, or plague. 
Enterovirus family of viruses like Coxsackie viruses, poliovirus and hepatitis A virus those live in the human digestive tract can spread from person to person, usually on unwashed hands and surfaces contaminated by faeces, where they can live for several days.
These germs can spread easily from one person to another – and have wide-reaching effects.
About 10 million U.S. adults (ages 18 - 69) were unable to work during 2002 due to health problems.
Salmonella infections (Typhoid etc.) are responsible for an estimated 1.4 million illnesses each year.
Infectious diseases cost the U.S. $120 billion a year. More than 160,000 people in the U.S. die yearly from an infectious disease.
Over 320.000 patients in the UK acquire one or more health care-associated infections during their stay in hospital of which 50.000 result in death, are transmitted via the hands.
The World Health Organization (WHO) recognizes the spread of diarrhoeal diseases as a serious global problem and estimates that each year, there are more than 2.2 million lives lost due to these infections, more than from malaria, HIV/AIDS and measles combined. The majority of these deaths are in children under 5 years of age.
As a consequence, this leads to prolonged patient suffering, longer confinement to bed and elevated treatment costs. In Great Britain, additional hospitalization costs of approximately £930 million (this is equivalent to approx. 1. 2 billion Euros) are calculated to be the result.




Unsuspected Source of infection: Germs are hiding everywhere
  • “The bulk of germs are hiding where you least suspect – playground equipment, the phone receiver, ATMS and elevator buttons.” 229,000 germs per square inch on frequently used faucet handles. 
  •  21,000 germs per square inch on work desks about 400 times more than the average toilet seat. 
  •  More germs at the kitchen sink than at the toilet. 
  •  1,500 on each square centimetre of hands.
 High on the worst list:
  • Work desk, Kitchen sink, Dishcloth, sponge 
  •  Garbage can, Refrigerator, Telephone receiver, Cell Phones 
  •  Bathroom doorknob, Keyboards, Escalator handrails 
  •  Shopping cart handles, Picnic tables, Pens, pencils and crayons 
  •  Remote controls, Light switches, Bathroom cups 
  •  The soap suspends the dirt and soils. 
  •  Many pets, such as dogs, cats, reptiles, rodents, and birds, carry germs that can be spread from animals to people.



Nosocomial infections:

Nosocomial infections, also called “hospital-acquired infections”, are the infections acquired during hospital care which are not present or incubating at admission. Infections occurring more than 48 hours after admission are usually considered nosocomial.
When you cough or sneeze, you send tiny germ-filled droplets into the air. Colds and flu usually spread that way. You contaminate your hand from these acts and handling patients and their body fluids. You transmit and contact disease to yourselves.

Hand Hygiene:
Washing your hands correctly is the best way to stop the spread of infections.  Eighty percent of common infections are spread by hands. Washing your hands at least five times a day has been shown to significantly decrease the frequency of colds, influenza (the “flu”) and other infections.

Good Hand washing Really Works!

The US Centers for Disease Control (CDC) confirms, “Handwashing is the single most important means of preventing the spread of infection.”
A Wirthlin study of 305 Detroit students washed four times a day resulting in 24% fewer colds and 51% less stomach upsets.
A Minnesota daycare provider reported that teachers helped the kids wash their hands every morning when they arrived and the staff disinfected all areas parents may have touched. Result was 50% fewer illnesses at those daycares. 

  • Covering your mouth and nose when you sneeze or cough. Sneeze or cough into your elbow, not your hands.
  • Cleaning your hands often - always before you eat or prepare food, and after you use the bathroom or change a diaper
  • Avoiding touching your eyes, nose or mouth
Hand washing is one of the most effective and most overlooked ways to stop disease. Soap and water work well to kill germs. Wash for at least 20 seconds and rub your hands briskly.

When:
  • After going to the toilet or changing diapers 
  •  After coughing or sneezing 
  •  After getting visible soil on hands 
  •  After handling raw meat/poultry or unwashed fruits and veggies 
  •  After playing with pets 
  •  After smoking, eating or drinking 
  •  After touching sores, lacerations or infected areas 
  •  After playing/working outside 
  •  After playing in water more than one person has used 
  •  After touching any animals
  • After handling shared objects like telephone, Key Board, Door Knob
  • After helping someone with a runny nose
  • Before and after caring for someone who is sick
  • Before performing first aid or applying a band-aid
  • When arriving at work or school
  • Before and after eating or feeding someone else
  • Before preparing food 
  •  Before handling foods 
  •  Before eating 
  •  Before giving medications 
  •  Before putting contacts in eyes 
  •  Before playing in water more than one person is using 
  •  Before touching ready-to-eat foods/snacks
  • Household or garden chemicals, or anything that could be contaminated — such as a cleaning cloth or soiled shoes
How to Wash Your Hands Correctly



·        Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap.
·         Lather your hands by rubbing them together with the soap. Be sure to lather the backs of your hands, between your fingers, and under your nails.
·          Scrub your hands for at least 20 seconds. Need a timer? Hum the "Happy Birthday" song from beginning to end twice.
·          Rinse your hands well under clean, running water.
·                                                                                                                 Dry your hands using a clean
                                                                                                              towel

 A word of Caution:
  • In public restrooms, consider using a paper towel to flush the toilet and open the door because toilet and door handles harbor germs. Throw the towel away after you leave. 
  • Keep in mind that antibacterial soap is not more effective at killing germs than is regular soap. Using antibacterial soap may even lead to the development of bacteria that are resistant to the product's antimicrobial agents — making it harder to kill these germs in the future. 
  •  Alcohol-based hand sanitizers can quickly reduce the number of microbes on hands in some situations, but sanitizers do not eliminate all types of germs. 
  • Although alcohol-based hand sanitizers can inactivate many types of microbes very effectively when used correctly, people may not use a large enough volume of the sanitizers or may wipe it off before it has dried. Furthermore, soap and water are more effective than hand sanitizers at removing or inactivating certain kinds of germs, like Cryptosporidium, norovirus, and Clostridium difficile. 
  • Alcohol-based hand rubs may be less effective against C. difficile; using soap and running water is recommended if there is an outbreak of C. difficile infection.
SEPARATE:

Don’t cross-contaminate one food with another:

Cross-contamination occurs when bacteria spread from a food to a surface . . . from a surface to another food . . . or from one food to another. 

You’re helping to prevent cross-contamination when you:

  • Separate raw meat, poultry, seafood and eggs from other foods in your grocery cart, grocery bags, and in your refrigerator.  Be sure to use the plastic bags available in the meat and produce sections of the supermarket. 
  • Use one cutting board for fresh produce and a different one for raw meat, poultry and seafood. 
  • Never place cooked food on a plate that previously held raw meat, poultry, seafood, or eggs.  
  • Don’t allow juices from meat, seafood, poultry, or eggs to drip on other foods in the refrigerator.  Use containers to keep these foods from touching other foods. 
  • Never re-use marinades that were used on raw food, unless you bring them to a boil first.
Take Home Message:





It is always better to prevent disease than to treat. Hand washing is proven, but least used means to prevent and control infectious diseases.
Let us spread the information to remain healthy, wealthy and wise.
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