Widal reaction Health Dictionary

A test introduced for the diagnosis of SYPHILIS by examination of the blood. It has now been largely supplanted by other, more speci?c tests.... wassermann reaction

(PCR) A method of rapidly copying DNA sequences so that they can be analysed.... polymerase chain reaction

Any undesirable or unwanted consequence of a preventive, diagnostic or therapeutic procedure.... adverse event / reaction

When a new drug is introduced, it has usually been studied only in relatively few patients – typically 1,500. If n patients have been studied, and no serious effects observed, there is still a chance of a serious adverse e?ect occurring in the general population as frequently as 3/n (1:500).

Adverse effects can be divided into types. First, those which are closely related to the concentration of the drug and accord with what is known of its PHARMACOLOGY. These so-called type A (augmented pharmacological) effects are distinguished from type B (bizarre) effects which are unpredictable, usually rare, and often severe. ANAPHYLAXIS is the most obvious of these; other examples include bone-marrow suppression with CO-TRIMOXAZOLE; hepatic failure (see HEPATITIS) with SODIUM VALPROATE; and PULMONARY FIBROSIS with AMIODARONE. A more comprehensive classi?cation includes reactions type C (chronic effects), D (delayed effects – such as teratogenesis or carcinogenesis) and E (end-of-dose effects – withdrawal effects). Examples of adverse reactions include nausea, skin eruptions, jaundice, sleepiness and headaches.

While most reported adverse reactions are minor and require no treatment, patients should remind their doctors of any drug allergy or adverse e?ect they have suffered in the past. Medical warning bracelets are easily obtained. Doctors should report adverse effects to the authorities – in the case of Britain, to the Committee on Safety of Medicines (CSM), using the yellow-card reporting machinery.... adverse reactions to drugs

A serological test used to detect antibodies in the diagnosis of typhoid. Antigens detected are the O (somatic), H (flagellar) and Vi (virulence) antigens.... widal test

Herbalists, phytotherapists, other practitioners and companies are required by the Committee on Safety of Medicines to report all adverse reactions associated with herbal products used in the treatment of disease in the UK within one month. Adverse reactions to over-the-counter alternative medicines should be reported using the yellow card scheme. (CSM., Current Problems 1986, No 16:477.) ... adverse reactions

(Eisenmenger syndrome) a condition in which *pulmonary hypertension is associated with a *septal defect, so that blood flows from the right to the left side of the heart or from the pulmonary artery to the aorta. This allows blue blood, poor in oxygen, to bypass the lungs and enter the general circulation. This reduces the oxygen content of the arterial blood in the aorta and its branches, resulting in a patient with a dusky blue appearance (*cyanosis) and an increased number of red blood cells (*polycythaemia). There is no curative treatment at this stage, but the patient may be helped by the control of heart failure and polycythaemia. The condition may be prevented by appropriate treatment of the septal defect in early childhood before irreversible pulmonary hypertension develops. [V. Eisenmenger (1864–1932), German physician]... eisenmenger reaction

a method of demonstrating the presence of DNA in cell nuclei. The tissue section under investigation is first hydrolysed with dilute hydrochloric acid and then treated with *Schiff’s reagent. A purple coloration develops in the presence of DNA. [R. Feulgen (1884–1955), German chemist]... feulgen reaction

see Jarisch-Herxheimer reaction.... herxheimer reaction

(Herxheimer reaction) exacerbation of the symptoms of syphilis that may occur on starting antibiotic therapy for the disease. The effect is transient and requires no treatment. [A. Jarisch (1850–1902), Austrian dermatologist; K. Herxheimer (1861–1944), German dermatologist]... jarisch–herxheimer reaction

a test for syphilis, in which antibodies specific to the disease are detected in a sample of the patient’s blood by means of a *precipitin reaction. This test is not as reliable as some. [R. L. Kahn (20th century), US bacteriologist]...  kahn reaction

an aggravation of lumps on the skin caused by *leprosy, accompanied by fever and malaise.... lepra reaction

a histochemical test for proteins, in which ninhydrin (triketohydrindene hydrate) is boiled with the test solution and gives a blue colour in the presence of amino acids and proteins.... ninhydrin reaction

(PAS reaction) a test for the presence of glycoproteins, polysaccharides, certain mucopolysaccharides, glycolipids, and certain fatty acids in tissue sections. The tissue is treated with periodic acid, followed by *Schiff’s reagent. A positive reaction is the development of a red or magenta coloration.... periodic acid–schiff reaction

a reaction in which antibodies against the bacterium Streptococcus pneumoniae combine with the bacterial capsule, which becomes swollen and visible to light microscopy.... quellung reaction

(in psychoanalysis) a *defence mechanism by which unacceptable unconscious ideas are replaced in consciousness by their opposites. For instance, a man might make an ostentatious show of affection to someone for whom he has an unconscious hatred.... reaction formation

a diagnostic test for typhus. A sample of the patient’s serum is tested for the presence of antibodies against the organism Proteus vulgaris. Although this relatively harmless organism is not the cause of typhus, it possesses certain antigens in common with the causative agent of the disease and can therefore be used instead of it in laboratory tests. Typhus is suspected if antibodies are found to be present. [E. Weil (1880–1922), German physician; A. Felix (1887–1956), Czech bacteriologist]... weil–felix reaction