WEBVTT 00:00:00.000 --> 00:00:36.200 [Music] 00:00:36.200 --> 00:00:40.500 [Narrator:] Rubella testing in the small hospital laboratory. 00:00:40.500 --> 00:00:43.666 Serology laboratories, both large and small, 00:00:43.666 --> 00:00:48.699 are constantly being deluged with requests for rubella antibody testing. 00:00:48.700 --> 00:00:51.566 Technology is now available for determination 00:00:51.566 --> 00:00:59.299 of immune status to rubella, diagnosis of postnatal rubella, and diagnosis of congenital rubella. 00:00:59.300 --> 00:01:04.033 We will discuss several of the standardized and clinical methods available, 00:01:04.033 --> 00:01:08.566 along with the clinical settings in which each would be appropriate. 00:01:08.566 --> 00:01:12.332 In school-age children, rubella, or German measles, 00:01:12.333 --> 00:01:15.433 is usually a self-limiting disease characterized by 00:01:15.433 --> 00:01:21.899 upper respiratory involvement, lymphoadenopathy, and an erythematous rash. 00:01:21.900 --> 00:01:25.300 To determine if an acute infection is in progress, 00:01:25.300 --> 00:01:30.866 the most widely used procedure is the hemagglutination inhibition, or HAI. 00:01:30.866 --> 00:01:33.499 Hemagglutination inhibition is based on 00:01:33.500 --> 00:01:36.233 the serological principle that the agglutination 00:01:36.233 --> 00:01:39.533 of red blood cells by rubella antigen can be blocked 00:01:39.533 --> 00:01:45.166 or inhibited by antibody and a serum specificfor that antigen. 00:01:45.166 --> 00:01:48.599 A treatment process is used to remove serum inhibitors, which are not 00:01:48.600 --> 00:01:51.933 specific rubella antibody. 00:01:51.933 --> 00:01:54.299 By testing ever-decreasing dilutions 00:01:54.300 --> 00:01:57.333 of a serum against a constant amount of antigen, 00:01:57.333 --> 00:02:00.899 the antibody content of the serum can be determined. 00:02:00.900 --> 00:02:04.233 Complications of the technique are one, 00:02:04.233 --> 00:02:07.033 non-specific inhibitors of agglutination 00:02:07.033 --> 00:02:09.599 may exist in normal serum, which block 00:02:09.600 --> 00:02:12.966 the viral hemagglutination by obscuring sites 00:02:12.966 --> 00:02:16.732 either on the red blood cell or on the virus. 00:02:16.733 --> 00:02:21.333 Test serum may contain hemagglutinating substances. 00:02:21.333 --> 00:02:25.299 To be truly diagnostic for acute rubella infection, 00:02:25.300 --> 00:02:30.900 an established format should be followed for drawing the HAI test specimens. 00:02:30.900 --> 00:02:35.833 One, the HAI test must be run on paired sera. 00:02:35.833 --> 00:02:38.866 Acute serum should be taken early in the infection, 00:02:38.866 --> 00:02:43.199 preferably no later than three days after clinical onset. 00:02:43.200 --> 00:02:49.966 A second specimen should be drawn between two to three weeks after the onset of clinical symptoms. 00:02:49.966 --> 00:02:55.666 Two, the paired sera are then assayed in the same test run. 00:02:55.666 --> 00:03:02.966 Three, a four-fold or greater rise in titer is diagnostic of recent rubella infection. 00:03:02.966 --> 00:03:07.666 There is considerable variability in the antibody titers maintained during life. 00:03:07.666 --> 00:03:13.299 Therefore, a diagnosis cannot be made on a single serum sample. 00:03:13.300 --> 00:03:20.800 Four, stable or falling titer can only be interpreted as infection in recent past. 00:03:20.800 --> 00:03:26.300 When congenital infection is suggested in a neonate, paired sera should be taken as follows. 00:03:26.300 --> 00:03:30.966 One. One specimen is drawn from both the mother and the infant 00:03:30.966 --> 00:03:33.499 when the infant is less than six months of age. 00:03:33.500 --> 00:03:37.933 Two, a second specimen is taken from both the infant and mother 00:03:37.933 --> 00:03:42.033 when the infant is 6 to 12 months old. 00:03:42.033 --> 00:03:44.499 If when performing hemagglutination inhibition testing, 00:03:44.500 --> 00:03:50.133 the rubella antibody of the infant is present in a stable titer amount, 00:03:50.133 --> 00:03:53.366 possible congenital infection is indicated. 00:03:53.366 --> 00:03:59.666 Also, if the mother does not have rubella antibodies or has a very low titer, 00:03:59.666 --> 00:04:02.999 it is unlikely that the baby had congenital infection. 00:04:03.000 --> 00:04:06.700 A second approach to determining possible congenital infection 00:04:06.700 --> 00:04:11.800 is to demonstrate rubella-specific IgM antibody in the infant serum. 00:04:11.800 --> 00:04:16.933 Such IgM is present only in primary rubella infection. 00:04:16.933 --> 00:04:22.799 It is short-lived and begins to decrease a few weeks after the infection. 00:04:22.800 --> 00:04:26.600 The immunoglobulin in serum is separated by a sucrose density gradient, 00:04:26.600 --> 00:04:31.966 and the rubella-specific IgM is then measured by HAI. 00:04:31.966 --> 00:04:38.399 Only when rubella-specific IgM is found can one be sure of recent rubella infection. 00:04:38.400 --> 00:04:43.566 Passive hemagglutination, or PHA, is another rubella testing procedure 00:04:43.566 --> 00:04:48.399 which has been standardized and is routinely used in the serology laboratory. 00:04:48.400 --> 00:04:53.100 It is easily performed and much quicker than hemagglutination inhibition. 00:04:53.100 --> 00:05:00.000 Passive hemagglutination will begin picking up antibody levels about two weeks later than the HAI. 00:05:00.000 --> 00:05:07.866 A positive PHA indicates that the serum sample has HAI titer of 1 to 8 or greater. 00:05:07.866 --> 00:05:12.899 Passive hemagglutination is used primarily as a screening technique. 00:05:12.900 --> 00:05:18.566 It allows for an easy and quick method for determination of immune status. 00:05:18.566 --> 00:05:25.599 PHA tests that are positive indicate that the patient has a protective level of rubella antibody. 00:05:25.600 --> 00:05:30.600 If the PHA test is negative, it should be repeated by HAI. 00:05:30.600 --> 00:05:39.100 If the HAI titer is less than 1 to 8, the patient has insufficient rubella antibody to protect him from infection. 00:05:39.100 --> 00:05:46.766 Women of childbearing age who are sero-negative should be vaccinated with live virus vaccine. 00:05:46.766 --> 00:05:52.099 Due regard should be taken for the potential dangers of vaccination during pregnancy. 00:05:52.100 --> 00:05:59.400 Many physicians determine the rubella antibody status of pregnant women at the patient's first prenatal visit. 00:05:59.400 --> 00:06:05.666 Those without antibody are monitored through early pregnancy for sero conversion. 00:06:05.666 --> 00:06:11.532 The passive hemagglutination test incorporates rubella antigen onto erythrocytes, 00:06:11.533 --> 00:06:16.599 which will agglutinate in the presence of rubella antigen in the patient's serum. 00:06:16.600 --> 00:06:20.900 The test is performed in the V-bottom microtiter plate. 00:06:20.900 --> 00:06:26.200 If the patient has rubella antibody, the agglutinated antigen antibody complex 00:06:26.200 --> 00:06:31.033 settles to the bottom of the V-shaped plate in a dispersed pattern. 00:06:31.033 --> 00:06:35.733 If little or no agglutination has occurred, the red cells slide to the bottom, 00:06:35.733 --> 00:06:39.399 forming a sharp compact button. 00:06:39.400 --> 00:06:45.000 The V-plate is read by using a mirrored microtiter plate reader. 00:06:45.000 --> 00:06:48.966 In conclusion, there are many sophisticated techniques 00:06:48.966 --> 00:06:54.099 for rubella testing available on the market, some old, some new. 00:06:54.100 --> 00:06:56.900 Some techniques used other than the ones mentioned here are 00:06:56.900 --> 00:07:07.700 radioimmunoassasy, enzyme-linked immunosorbent assay, fluorometry orIFA, and hemolysin-in-gel. 00:07:07.700 --> 00:07:10.933 These tests may grow to be the techniques of the future, 00:07:10.933 --> 00:07:15.833 but because of their standardization, hemagglutination inhibition, or HAI, 00:07:15.833 --> 00:07:19.066 and passive hemagglutination, PHA, 00:07:19.066 --> 00:07:22.466 should be the first choice in rubella immunity screening 00:07:22.466 --> 00:07:26.732 until the superiority of other methods has been proven. 00:07:26.733 --> 00:07:33.199 [Music] 00:07:33.200 --> 00:07:36.500 [Mark-Maris] 00:07:36.500 --> 00:08:23.800 [End of film]