SEROLOGY

VDRL TEST VENERAL DISEASE RESEARCH LABARTORY TEST VDRL T EST VDRL is a serological test perform for the diagnosis of syphilis. PRINCIPLE A phospholipid i.e cardiolipin, derived from beef heart muscle together with cholesterol and lecithin is used as an antigen. After mixing the antigen with patient serum, the reaction is accelerated by rotatory agitation. The antigen react with antibodies produced and form floccules. These floccules can be observed with naked eye, hand lens or under a low power objective of a microscope. EQUIPMENT VDRL test slide—a glass slide with 12 paraffin or ceramic rings of approx. 14mm inside diameter. Hypodermic needles without bevels Syringe 1-2 ml 30ml flat glass stoppered Narrow mouth bottle approx. 35mm in diameter PRECAUTION Use clean and dry glass ware. Allow all reagents and samples to reach at room temperature before starting the test. Carry out the test at room temperature. PREPARATION OF PATIENT SERUM Heat clear serum sample in a water bath at 56c for 30 min. examine all serum samples after removing from the water bath and those found to contain particulate debris should be recentrifuged. Allow the serum to cool to room temperature. REAGENTS VDRL reagent Buffered saline diluent Positive control serum negative control serum PREPARATION OF WORKING SOLUTION 1. Pipette 0.4 ml of Buffered saline diluent into a glass stoppered bottle. 2. Add 0.5ml of VDRL reagent from the lower half of 1.0ml pipette directly to the buffered saline diluent while continuous and gentle shaking. 3. Continue rotation of bottle for 10 more seconds. 4. Now add 4.1ml of buffered saline diluent to the bottle, close the bottle and shake it for approximately 10 seconds. PRELIMINARY TESTING OF WORKING ANTIGEN SUSPENSION Each time the working antigen suspension is prepared, it has to be tested with positive and negative controls. The working antigen suspension should give expected typically reactive and non-reactive results respectively. The antigen control should be smooth in appearance with antigen particles well dispersed. Do not use working antigen suspension i0f 1it does not give satisfactory performance in the preliminary testing. STORAGE AND STABILITY VDRL antigen and buffered saline diluent are to be stored In a cool and dark place at room temperature. The control sera are stable at 2-8C till the expiry date mentioned. PROCEDURE QUALITATIVE TEST Pipette 0.05ml of patient’s inactivated serum into the concavity of VDRL slide. Pipette 0.05ml each of positive and negative control sera into other two concavities of the VDRL slide. Add one drop of the working antigen suspension to each of the above concavities, with calibrated 23-gauge needle. Rotate the slide for 4 min on a flat surface with hand or on a VDRL rotator. Read the test immediately under a low power objective of a microscope. QUANTITATIVE TEST Prepare different dilutions of test serum in test tubes in the range of 1:2, 1:4, 1:8, 1:16, 1:32 or more with normal saline. Transfer 0.05ml of each of the above SERA into separate concavities of VDRL slide. With the help of 23 gauge size needle add one drop of working antigen suspension to each of the above concavities. Rotate the slide for 4 min with hand or on a VDRL rotator. Read the test immediately under a low power objective of a microscope. NOTE the results of controls should be satisfactory for validating the result of tests. INTERPRETATIONS The antigen particles are seen as small fusiform needles which remain more or less depressed in case of non reactive serum and aggregate into clumps with reactive serum. The conclusions can be drawn from the observation as follows: LIMITATIONS Prozone phenomenon Acute or chronic infections e.g malaria, leprosy, infectious mononucleasis, upper respiratory diseases, collagen and immunologic disorders like rheumatoid arthritis and lupus erythematosus can produce FALSE_POSITIVE test results.

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