Gaydos C A, Eiden J J, Oldach D, Mundy L M, Auwaerter P, Warner M L, Vance E, Burton A A, Quinn T. 96%, and that of the SeroCp-EIA was 92%. Specificity was high for those methods, but modifications of diagnostic criteria were made to several of the checks. The basis for these modifications and supportive data are offered. Infections of were detected in individuals from 8 to 83 years of age. Two peaks in the incidence of such infections were observed: one among young teenagers and a second in adults 30 to 45 years of age, related to parents of young teen-agers. The checks were equally sensitive in different age organizations. Reinfections seemed to be rare. Serological diagnosis has been important to unravel the medical manifestations of acute infections by and was acknowledged and illness by this fresh agent could be confidently diagnosed from the microimmunofluorescence (MIF) test, many instances previously detected from the CF test and thought to be instances of ornithosis were found to in fact be infections by (12, 18). Even though CF test can detect acute infections by and to describe the prevalence of L-779450 such infections. The performance of the test depends on several factors, including the antigen preparations used and the experience of the person reading the test. The test has been questioned for different reasons. Some have found it unspecific during acute infections due to cross-reactive antibodies (5, 17). Others have questioned its ability to discriminate acute infections, either by being nonreactive where additional checks suggest illness (3, 7, 9) or by identifying cases which cannot be confirmed by additional means or which seem unlikely for additional reasons (10, 11, 14, 15). Serological checks in an enzyme-linked immunoassay (ELISA) format might conquer some of the potential problems with the MIF test. Three new checks have been evaluated in this study and compared to the MIF and CF checks for the serological analysis of acute infections by organisms with (SeroCp-EIA) or without (LOY-EIA) LPS. MATERIALS AND METHODS Patients. During an epidemic of infections by were from Labsystems OY (Helsinki, Finland). With this test the and antigens have been treated to remove the LPS antigen, which is definitely, L-779450 however, retained in the antigen. Chlamydial immunoglobulin G (IgG), IgA, and IgM antibodies were identified. All IgM reactions were confirmed after the IgG antibodies had been eliminated with RF Absorbent (Behringwerke, Marburg, Germany). Fourfold titer increases of IgG and/or IgA and/or a titer of 16 in IgM was regarded as diagnostically significant. Large titers of IgG or IgA that did not change between acute- and convalescent-phase sera were not considered diagnostic per se and will be discussed below. rEIA. The rEIA packages were kindly provided by the Medac Organization (Wedel, Germany). The test is based on a chemically altered recombinant LPS from chlamydia (6). IgG, IgA, and IgM antibodies to the chlamydial LPS are identified separately with this test. IgG antibodies are eliminated before L-779450 measuring IgM antibodies to minimize the risk of false-positive reactions due to rheumatoid factor. Serum pairs with variations in optical denseness ideals for IgG or IgA of more than 0.3 or with ideals of >2.0 were titrated in two, three, or four methods to determine the titer variations. Titers were determined according to the manufacturer’s instructions. A threefold switch of titer of either IgG or IgA or a twofold switch of both IgG and IgA was regarded as diagnostically significant (19). IgM titers of 200 or more were accepted like a diagnostic sign, although a positive titer of 50 should be considered positive according to the manufacturer. LOY-EIA. The LOY-EIAs (Labsystems OY, Helsinki, Finland) for IgG, IgA, and IgM antibodies are indirect solid-phase EIAs based on an antigen from devoid of LPS. The analysis with the LOY-EIA was performed by Tamara Tuuminen, Labsystems OY, Helsinki, Finland, without knowledge of the results from the additional checks. The results for IgG and IgA are indicated as enzyme immunounits (EIU), which are determined as: (= 130 for the IgG EIA and = L-779450 30 for the IgA EIA. A level of 30 EIU for IgG is considered the limit of detection (related to a titer of 32 in the MIF assay), and a level RIEG of 8 EIU in the IgA EIA is the related limit of detection (titer of 8 in the MIF assay). The criterion for any diagnostically significant switch of EIU ideals for IgG and IgA is definitely a 1.5-fold change of EIU in the zones below 130 EIU (for IgG) and 50 EIU (for IgA). When the 1st sample shows.