Evaluation of new monoclonal antibody-based latex agglutination test for detection of cryptococcal polysaccharide antigen in serum and cerebrospinal fluid.

We evaluated the performance of CRYPTO-LEX (Trinity Laboratories, Inc., Raleigh, N. C.), a new mouse immunoglobulin M monoclonal antibody latex agglutination reagent which reacts with the capsular polysaccharide of the four serogroups of Cryptococcus neoformans. This test was compared with CALAS (Meridian Diagnostics, Cincinnati, Ohio) for the ability to detect cryptococcal antigen in serum and cerebrospinal fluid (CSF). A total of 580 clinical specimens (327 serum and 253 CSF samples), primarily from human immunodeficiency virus-infected patients, were tested in this study. Sixty-seven specimens (44 serum and 23 CSF samples) were positive for cryptococcal antigen with both tests, and 511 (282 serum and 229 CSF samples) were negative. The two latex reagents agreed for 326 of 327 serum specimens (44 positives and 282 negatives). One serum specimen with a titer of 1:2 was CALAS positive but CRYPTO-LEX negative. The titer correlation coefficient for the two tests was 0.884 when two highly discordant serum specimens were eliminated from analysis of the data. The two latex tests agreed for 252 of 253 CSF specimens (23 positives and 229 negatives). One specimen with a titer of 1:2 was positive with CALAS and negative by CRYPTO-LEX. The correlation coefficient of the two tests for CSF titers was 0.886. The sensitivity and specificity of CRYPTO-LEX were 97 and 100%, respectively, with a 99.6% correlation with CALAS. These data show that the performance of CRYPTO-LEX is comparable to that of CALAS for detection of cryptococcal antigen in serum and CSF

Evaluation of new monoclonal antibody-based latex agglutination test for detection of cryptococcal polysaccharide antigen in serum and cerebrospinal fluid

We evaluated the performance of CRYPTO-LEX (Trinity Laboratories, Inc., Raleigh, N. C.), a new mouse immunoglobulin M monoclonal antibody latex agglutination reagent which reacts with the capsular polysaccharide of the four serogroups of Cryptococcus neoformans. This test was compared with CALAS (Meridian Diagnostics, Cincinnati, Ohio) for the ability to detect cryptococcal antigen in serum and cerebrospinal fluid (CSF). A total of 580 clinical specimens (327 serum and 253 CSF samples), primarily from human immunodeficiency virus-infected patients, were tested in this study. Sixty-seven specimens (44 serum and 23 CSF samples) were positive for cryptococcal antigen with both tests, and 511 (282 serum and 229 CSF samples) were negative. The two latex reagents agreed for 326 of 327 serum specimens (44 positives and 282 negatives). One serum specimen with a titer of 1:2 was CALAS positive but CRYPTO-LEX negative. The titer correlation coefficient for the two tests was 0.884 when two highly discordant serum specimens were eliminated from analysis of the data. The two latex tests agreed for 252 of 253 CSF specimens (23 positives and 229 negatives). One specimen with a titer of 1:2 was positive with CALAS and negative by CRYPTO-LEX. The correlation coefficient of the two tests for CSF titers was 0.886. The sensitivity and specificity of CRYPTO-LEX were 97 and 100%, respectively, with a 99.6% correlation with CALAS. These data show that the performance of CRYPTO-LEX is comparable to that of CALAS for detection of cryptococcal antigen in serum and CSF.</jats:p

Quality assurance study of bacterial antigen testing of cerebrospinal fluid

Bacterial antigen testing (BAT) of cerebrospinal fluid (CSF) by latex agglutination is a low-yield procedure in patients whose CSF specimens have normal laboratory parameters. Between August 1992 and August 1994, we evaluated 287 bacterial antigen (BA) test requests to determine whether yields could be improved and whether patient costs could be reduced by cancelling BAT for those patients with normal CSF parameters (cell count, protein, glucose) after consultation with physicians. A total of 171 (68%) BA tests were canceled by this approach. None of these CSF specimens was culture positive for an organism detectable by BAT. Of the remaining 116 CSF specimens tested, only 3 were positive by BAT, one each for Neisseria meningitidis, Streptococcus pneumoniae, and group B streptococcus. Only 43 of the CSF specimens tested had at least two abnormal parameters; the 3 positive CSF specimens were included in this group. In light of the low rate of positivity, the number of BA tests can be further reduced by establishing criteria that must be met before a CSF specimen is accepted for BAT. After review of our data and the literature concerning this topic, we concluded that only specimens with leukocyte counts of &gt; or = 50 cells per mm3 should be tested. Of 287 specimens evaluated in our study, only 36 met this criterion, including the 3 BA-positive specimens. Enacting such a restriction would have reduced the total number of BA tests by 251 (87%) without compromising patient care. A laboratory cost savings of $6,500 per year would have been realized, with a substantial reduction in the cost per positive test. Patient charges would have been reduced by$12,500 per year.</jats:p

Quality assurance study of bacterial antigen testing of cerebrospinal fluid.

Bacterial antigen testing (BAT) of cerebrospinal fluid (CSF) by latex agglutination is a low-yield procedure in patients whose CSF specimens have normal laboratory parameters. Between August 1992 and August 1994, we evaluated 287 bacterial antigen (BA) test requests to determine whether yields could be improved and whether patient costs could be reduced by cancelling BAT for those patients with normal CSF parameters (cell count, protein, glucose) after consultation with physicians. A total of 171 (68%) BA tests were canceled by this approach. None of these CSF specimens was culture positive for an organism detectable by BAT. Of the remaining 116 CSF specimens tested, only 3 were positive by BAT, one each for Neisseria meningitidis, Streptococcus pneumoniae, and group B streptococcus. Only 43 of the CSF specimens tested had at least two abnormal parameters; the 3 positive CSF specimens were included in this group. In light of the low rate of positivity, the number of BA tests can be further reduced by establishing criteria that must be met before a CSF specimen is accepted for BAT. After review of our data and the literature concerning this topic, we concluded that only specimens with leukocyte counts of > or = 50 cells per mm3 should be tested. Of 287 specimens evaluated in our study, only 36 met this criterion, including the 3 BA-positive specimens. Enacting such a restriction would have reduced the total number of BA tests by 251 (87%) without compromising patient care. A laboratory cost savings of $6,500 per year would have been realized, with a substantial reduction in the cost per positive test.(ABSTRACT TRUNCATED AT 250 WORDS

Parent ion resolution in linked scans for dissociations occurring in the first field-free region of sector mass spectrometers

A frequently employed means of studying reactions of ions under high energy collisional activation conditions involves linked scanning a double-focusing mass spectrometer to detect product ions formed in the first field-free region. Experiments have demonstrated that the effective resolution of the parent ion varies during the course of a product ion scan, and this variation is attributed to the kinetic energy released during dissociation. Carefully generated Lacey-Macdonald ion intensity diagrams accurately reflect the dissociation events occurring in various regions of sector mass spectrometers. Consideration of such diagrams leads to an understanding of the noted phenomena and allows the derivation of an expression for the effective parent ion resolution. Furthermore, the approach predicts that parent ion resolution varies during constant neutral loss scans and that the relatively poor resolution (and its variation) can provide particularly misleading data. Results from product ion scans with stable isotope-labeled compounds and constant neutral loss scans with rubidium bromide and stable isotope-labeled peptide derivatives were consistent with the theoretical prediction

Species-dependent post-translational modification and position 2 allelism: effects on streptococcal superantigen SSA structure and V beta specificity.

Abstract Epidemiologic and molecular population genetic analyses support a role for superantigens (SAg) in the pathogenesis of severe staphylococcal and streptococcal infections. To investigate how variations in SAg structure influence immunomodulatory activity, we examined the biochemical and functional properties of two allelic variants of streptococcal SAg SSA that differ at position 2. Mass spectrometry revealed both recombinant (Escherichia coli) and native (Streptococcus pyogenes) SSA allelic variants to have significantly larger molecular masses than predicted by primary sequence alone and provided evidence that the proteins were modified by the addition of biochemical moieties, a phenomenon that has not been described for related SAg. Furthermore, the molecular masses of native and recombinant SSA were not the same; SSA was differentially post-translationally modified by the two bacterial genera. The substitution of E. coli-dependent processing for that of S. pyogenes altered both protease digestion and V beta specificity, suggesting that recombinant SAg from E. coli may not accurately represent the native toxin. In addition, the observation that SSA allelic variants differed in V beta specificity supports a role for position 2 in SSA-TCR interactions. That SSA position 2 contributes to V beta specificity could not have been predicted from functional or crystallographic studies of other SAg and suggests that SSA may adopt unique interactions with TCR and/or MHC class II molecules. Determining the structural basis for these differences should offer additional clues to the manner in which SAg exert their effects on the immune system during infection and may allow the designing of SAg mutants with specific quantitative and qualitative immunomodulatory properties.</jats:p