Differential Diagnosis

Differential diagnosis: The process of weighing the probability of one disease versus that of other diseases possibly accounting for a patient's illness. The differential diagnosis of rhinitis (a runny nose) includes allergic rhinitis (hayfever), the abuse of nasal decongestants and, of course, the common cold. In medicine, differential diagnosis (sometimes abbreviated DDx, ddx, or ΔΔ) is the systematic method healthcare providers use to identify the disease causing a patient's symptoms. In other words, part of diagnosis is attempting to narrow down the list of possible diagnoses until one emerges as the best. The term differential evolves from the word differences. The concept of differential diagnosis involves observing and discovering signs and symptoms, then progressively considering the most likely illnesses, then continuously narrowing down the possible diagnoses, eliminating one after another, until one is left with only one specific diagnosis for the patient's signs and symptoms. Differential Diagnosis is the process whereby a given condition or circumstance, called the presenting problem or chief complaint, is examined in terms of underlying causal factors and concurrent phenomena as discerned by appropriate disciplinary perspectives and according to several theoretical paradigms or frames of reference, and compared to known categories of pathology or exceptionality. Differential diagnosis allows the physician to: 1. more clearly understand the condition or circumstance 2. assess reasonable prognosis 3. plan treatment or intervention for the condition or circumstance 4. enable the patient and the family to integrate the condition or circumstance into their lives, until the condition or circumstance may be ameliorated, if possible. If the patient's condition does not improve, the diagnosis must be reassessed. The method of differential diagnosis was first suggested for use in the diagnosis of mental disorders by Emil Kraepelin. It is more systematic than the old-fashioned method of diagnosis by gestalt (impression).[citation needed] The method of differential diagnosis is based on the idea that you begin by first considering the statistically more probable diagnoses. Medical students are taught the adage, "When you hear hoof beats, think horses, not zebras." It means that only after more probable diagnoses are ruled out do the somewhat less likely ones considered, and so forth. It used to be that doctors ordered only particular blood tests, but now the standard is a full blood chemistry profile which can speed up the process of diagnosis as well as uncover sub-clinical conditions. With the advent of better radiological studies like MRI and the wider use of nuclear medicine, it has become more likely that there will be unexpected findings that will be further studied, despite the fact that the findings will not be supported by further investigation. They are a valuable tool, but not infallible. It still often takes a physicians or medical team to track down either a more common illness with a rare presentation or a rare illness with symptoms suggestive of many other conditions. Sometimes a definitive diagnosis might take years. The term differential diagnosis also refers simply to a list of the most common causes of a given symptom, or a list of disorders similar to a given disorder. Prognosis (older Greek πρόγνωσις, modern Greek πρόγνωση - literally fore-knowing, foreseeing) is a medical term denoting the doctor's prediction of how a patient's disease will progress, and whether there is chance of recovery. Since the 20th century, the word has been increasingly used in non-medical contexts as well, for example in corporate finance.

Disease and Prognostic Indicators In medicine today, doctors search for methods of predicting how a patient (given their condition) may respond to treatment. Symptoms and tests may indicate favorable treatment with standard therapies. Likewise, a number of symptoms, health factors, and tests may indicate a less favorable treatment result with standard treatment - this may indicate that a more aggressive treatment plan may be desired. Two areas where this type of prognosis prediction, or the use of prognostic indicators, is with Hodgkin's lymphoma and Non-Hodgkin lymphoma. Specifically with Non-Hodgkin lymphoma, physicians have developed the International Prognostic Index to predict patient outcome. Prognostic scoring is also used for other cancer outcome predictions. A Manchester score is an indicator of prognosis in small cell lung cancer. Other medical areas prognostic indicators are used is in Drug-Induced Liver Injury (DILI) (Hy's Law) and use of an exercise stress test as a prognostic indicator after myocardial infarction. ASPHYXIANTS: A condition in which an extreme decrease in the concentration of oxygen in the body accompanied by an increase in the concentration of carbon dioxide leads to loss of consciousness or death. Asphyxia can be induced by choking, drowning, electric shock, injury, or the inhalation of toxic gases.

An effective dose in pharmacology is the amount of drug that produces a therapeutic response in 50% of the people taking it, sometimes also called ED-50. In radiation protection it is an estimate of the stochastic effect that a non-uniform radiation dose has on a human. In pharmacology, effective dose is the minimal dose that produces the desired effect of a drug. The effective dose is often determined based on analysing the dose-response relationship specific to the drug. The dosage that produces a desired effect in half the test population is referred to as the ED-50, for "Effective dose, 50%". A lethal dose (LD) is an indication of the lethality of a given substance or type of radiation. Because resistance varies from one individual to another, the 'lethal dose' represents a dose (usually recorded as dose per kilogram of subject body weight) at which a given percentage of subjects will die.The most commonly-used lethality indicator is the LD50 (or LD50), a dose at which 50% of subjects will die. LD measurements are often used to describe the power of venoms in animals such as snakes. LD figures depend not only on the species of animal, but also on the mode of administration. For instance, a toxic substance inhaled or injected into the bloodstream may require a much smaller dosage than if the same substance is swallowed.LD values for humans are generally estimated by extrapolating results from testing on animals or on human cell cultures. One common form of extrapolation involves measuring LD on animals like mice or dogs, converting to dosage per kilogram of biomass, and extrapolating to human norms. While animal-extrapolated LD values are correlated to lethality in humans, the degree of error is sometimes very large. The biology of test animals, while similar to that of humans in many respects, sometimes differs in important aspects. For instance, mouse tissue is approximately fifty times less responsive than human tissue to the venom of the Sydney funnelweb. The square-cube law can also complicate the scaling relationships involved.