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Immunological Tests for Diagnosis of Disease and Identification of Molecules
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Antibody-coated latex beads can be used in agglutination or ELISA techniques to detect antigen in samples. In addition to simple tube or microtiter agglutination tests which are read visually, several devices have been developed for use of the principle of latex agglutination in tests that can be sold commercially and used by relatively untrained persons. Two tests using latex beads will be described: lateral flow immunoassay, an agglutination procedure, and vertical flow-through immunoassay, an ELISA procedure.
Infectious Diseases
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
Vas Novelli, Delane Shingadia, Huda Al-Ansari
A clinical diagnosis should be made. Blood and/or CSF cultures may be positive: blood cultures tend to be positive in 50% of cases, while CSF cultures are positive in 70%. Whole blood polymerase chain reaction (PCR) test for N meningitidis should also be obtained; this is a very sensitive test, especially in cases where antibiotics have been given. Cultures of petechial scrapings do not add anything to obtaining blood culture and a PCR test. Sensitivity is a problem with latex agglutination tests to detect antigen in CSF, serum and urine.
Disseminated Histoplasmosis, Coccidioidomycosis, And Cryptococcosis
Published in Lourdes R. Laraya-Cuasay, Walter T. Hughes, Interstitial Lung Diseases in Children, 2019
The diagnosis is established by the demonstration of Cryptococcus neoformans in sputum or biopsy specimens from the infected lung by direct histological examination and isolation in culture. In the disseminated form the organism may be found in spinal fluid, urine, skin lesions, bone marrow, and blood. The organism cannot be definitely identified unless it is cultured, but the unique, thick capsule provides a characteristic useful in direct histologic examinations. The capsule of the yeast may be revealed with an India ink preparation or by a mucicarmine stain. Specimens for culture should be inoculated onto several Sabourand dextrose agar plates, without cycloheximide. The cryptococcal antigen test is a useful diagnostic aid, especially if central nervous system infection exists, but it is less sensitive with cryptococcosis limited to the lung. This latex agglutination test can be applied to spinal fluid, pleural fluid, serum, or urine. Approximately 90% of patients with meningitis will have detectable cryptococcal polysaccharide antigen in the spinal fluid.
Strategies for the diagnosis and management of meningitis in HIV-infected adults in resource limited settings
Published in Expert Opinion on Pharmacotherapy, 2021
Marise Bremer, Yakub E Kadernani, Sean Wasserman, Robert J Wilkinson, Angharad G Davis
In CSF analysis, polymorph leucocytosis of >1000 cells/mm3 is the best discriminator between bacterial and other causes of meningitis [46,47]. CSF culture remains the gold standard with a sensitivity of 81% when compared by to Gram stain and polymerase chain reaction (PCR) [48]. A study on repeated CSF cultures after normal initial CSF showed an increased diagnostic yield in clinically deteriorating patients, either by new bacteriological growth or the emergence of cell abnormalities [49]. This can assist with confirming the diagnosis of BM in this subset of patients. Gram stain is a widely used, rapid test that is valuable in early diagnosis with a sensitivity of 97.5% when referenced to culture, but less affected than culture by antibiotic activity in the CSF [48]. Antigen detection by latex agglutination (LA) is rapid, but when compared to culture sensitivity is 66% [50]. In culture negative BM pre-treated with antibiotics LA was also negative in all samples [51], showing no added value compared to other rapid testing modalities. The ongoing development of PCR assays has shown sensitivities up to 100% [52] and detection in culture negative samples [53]. These tests are also becoming less expensive and time consuming [54].
Novel strategies for rapid identification and susceptibility testing of MRSA
Published in Expert Review of Anti-infective Therapy, 2020
Masako Mizusawa, Karen C Carroll
Once an organism grows on culture media, tests can be performed on the isolates to detect PBP2a, which along with the detection of mecA, is recognized as a ‘gold standard’ method for determining methicillin resistance. Both latex agglutination (LA) and immunochromatographic methods have been used to characterize isolates from culture plates and directly from positive blood culture bottles. Latex agglutination assays have been available for several decades. Early studies of LA demonstrated high sensitivity ranging from 88.3% to 100% and excellent specificity ranging from 95.2% to 100% [92–94]. While they performed well, there were several limitations to their performance that include not only subjective reading for interpretation of the agglutination, but the time required to perform the test and the need for a heavy bacterial inoculum [94].
Accuracy of two plasma antibody tests and faecal antigen test for non-invasive detection of H. pylori in middle-aged Caucasian general population sample
Published in Scandinavian Journal of Gastroenterology, 2018
Sabine Skrebinska, Ilva Daugule, Daiga Santare, Sergejs Isajevs, Inta Liepniece-Karele, Dace Rudzite, Ilze Kikuste, Aigars Vanags, Ivars Tolmanis, Juris Atstupens, Jin Young Park, Rolando Herrero, Marcis Leja
The latex-agglutination test is based on passive agglutination reaction between antigens and antibodies. The ELISA test, on the other hand, is based on the detection of antibodies by adding a marked enzyme. However, latex-agglutination method could be even easily applicable than ELISA method since no special equipment is required other than a spectrometer, which is generally available in clinical laboratories [7]. In addition, sample preparation is easier and allows the processing of hundreds of samples in a short time [7]. On the other hand, ELISA method requires special equipment and the reaction should be measured in an automated ELISA instrument.