Validity of an enzyme immunoassay for detection of Neisseria gonorrhoeae antigens

Evaluation of a urease-based confirmatory enzyme-linked immunosorbent assay for diagnosis of Neisseria gonorrhoeae

A new urease-based enzyme-linked immunosorbent assay utilizing novel monoclonal antibodies was evaluated for the culture confirmation of Neisseria gonorrhoeae, with 270 isolates of N. gonorrhoeae, 56 isolates of diverse Neisseria spp., and 29 Moraxella isolates. The test was highly specific (100.00%) and sensitive (97.83%). No cross-reactions were observed with any of the Neisseria or Moraxella isolates tested. Fifty percent (3 of 6) of the false-negative results were obtained with isolates of serovar IA-4, a serovar rarely encountered in North America.

Rapid diagnosis of common sexually transmitted diseases in adolescents: a review

Sexually transmitted diseases (STDs) represent a significant health problem for adolescents in the United States. As a result, clinicians from a number of disciplines, among them pediatrics and dermatology, may be called on to evaluate teenage patients with these infections. Traditionally, the diagnosis of many STDs has relied on isolation of the causative organisms in culture. While such procedures typically offer optimal diagnostic accuracy, they are often time consuming and expensive, and may not be widely available. In an attempt to remedy this, culture-independent techniques have been developed to permit more rapid and economical diagnosis of these important pathogens. The strengths and limitations of these methods must be understood, however, for the tests to be used effectively.

Evaluation of a prototype DNA probe test for the noncultural diagnosis of gonorrhea

A prototype, nonisotopic, chemiluminescent DNA probe test called the Gen-Probe PACE (Probe Assay-Chemiluminescence Enhanced) system for Neisseria gonorrhoeae (Gen-Probe, San Diego, Calif.) was compared with conventional Martin-Lewis culture medium in JEMBEC plates for the laboratory diagnosis of gonorrhea. This 2-h noncultural assay is based upon the use of an acridinium ester-labeled DNA probe. The rRNA-directed DNA probe hybridizes with the target rRNA, and the hybridized probe is separated from the unhybridized probe through the use of magnetic microparticles. The esterified acridinium is hydrolyzed from the hybridized probe by the addition of an alkaline hydrogen peroxide solution, resulting in the production of visible light which is measured in a luminometer. The amount of light generated is directly proportional to the amount of gonococcal target rRNA present in the sample. A total of 407 clinical specimens (203 urethral and 204 endocervical) were collected from high-risk walk-in patients attending a sexually transmitted disease clinic. Separate patient specimens were collected for culture on Martin-Lewis medium in JEMBEC plates and for DNA probe assay. Statistical analysis of the overall comparative results showed that the DNA probe assay had a sensitivity, specificity, and positive and negative predictive values of 93, 99, 97, and 99%, respectively, in a patient population with a gonococcal disease prevalence of 21%. The results of this comparative study showed that the prototype chemiluminescent DNA probe assay is a rapid and reliable noncultural alternative for the laboratory diagnosis of gonorrhea.

Rapid detection methods in microbiology: are they right for your office?

This article discusses some of the direct test methods for diagnosing Group A streptococcal pharyngitis, urinary tract infection, and the three most common sexually transmitted diseases: gonorrhea, Chlamydia, and Herpes simplex virus infection. Emphasis is placed on their practicality for the office setting as well as the limitations of the test methods in various patient populations.

Diagnosis of Neisseria gonorrhoeae and Chlamydia trachomatis infections using antigen detection methods

Rapid antigen detection methods have great potential value in managing sexually transmitted gonococcal and chlamydial infections. Ideally, such tests should be rapid, technically simple, inexpensive, accurate, and applicable to all sites of infection commonly sampled (cervix, urethra, pharynx). For gonorrhea, the Gram stain fulfills these criteria in men with symptomatic urethritis, but lacks sensitivity when used at other sites or in asymptomatic patients. Antigen detection for gonorrhea would thus be of greatest value in 1) the diagnosis of gonococcal cervical infections in women with mucopurulent cervicitis or pelvic inflammatory disease, 2) the diagnosis of gonococcal proctitis in homosexual men, and 3) in situations requiring lengthy specimen transport. Because culture confirmation of Chlamydia trachomatis infections is not widely available, antigen detection tests could be of great value in management of these infections. Major uses include 1) confirming infection in women with cervicitis, endometritis, and pelvic inflammatory disease; 2) screening for asymptomatic infections in high risk groups of women; and 3) confirmation of Chlamydia trachomatis infections in infants and in adult males. The currently available methods for diagnosis of gonococcal and chlamydial infection by antigen detection are reviewed herein. Continued experience with antigen detection tests in well defined populations having high and low risk of gonococcal and chlamydial infection is needed to more fully determine how best to utilize these assays.

Validity and cost-effectiveness of the Gonozyme test in the diagnosis of gonorrhea

Although bacterial culture is considered to provide the most definitive diagnosis of gonorrhea, it has limitations when specimens must be transported long distances. A study was carried out to evaluate the validity and cost-effectiveness of an alternative method of diagnosing gonorrhea, the Gonozyme test, a commercially available enzyme immunoassay. Urogenital specimens from 100 men and 100 women with symptoms suggestive of or a history of exposure to gonorrhea were tested for the presence of Neisseria gonorrhoeae by means of bacterial culture and for gonococcal antigen with the Gonozyme test. The specimens from the men were also examined by means of microscopy of Gram-stained smears. The sensitivity and specificity of the Gonozyme test with reference to culture results were 95.6% and 97.4% respectively in the men and 84.2% and 98.7% in the women. The predictive value of a positive result was 91.6% in the men and 94.1% in the women, and the predictive value of a negative result 98.6% in the men and 96.3% in the women. The cost-effectiveness of the Gonozyme test was higher than that of bacterial culture in this population, which had a high prevalence rate of gonorrhea (23% in the men and 19% in the women). The Gonozyme test would be an adequate alternative to culture for the diagnosis of gonorrhea and contact tracing in areas far from diagnostic laboratories.

Enzyme-linked immunoassays for the detection of microbial antigens and their antibodies

Antibodies could be labeled with enzymes for use in histochemical staining procedures by enzyme-immunoassay (EIA). The use of EIA is an extension of previously used serological tests, using enzyme-labeled antibody or antigen to determine antibody content. Direct detection of antigen by EIA represents a more dramatic departure from previous methods based on culture. Also, the method has enabled detection of infectious agents that are difficult to cultivate, such as hepatitis A virus and rotavirus, or agents that cannot be cultivated, such as hepatitis B. The use of EIA tests for detection of microbial antigens provides an alternative to culture as a means for direct identification of a specific microbial agent. It also provides a means to detect microbial agents which have not been successfully propagated. The detection of circulating antigen or detection of antigen in other body fluids by EIA is more difficult than detection of antibody because of the sensitivity required, and because of interfering substances in specimens such as feces and respiratory secretions. For this reason, very few antigen detection assays have the sensitivity and specificity required to be used as a primary diagnostic test. The number of tests that have been developed, however, is impressive and because of the possibilities for rapid, specific diagnosis, the interest in antigen detection by EIA remains high.

Evaluation of Gonozyme, an enzyme immunoassay for the rapid diagnosis of gonorrhea

A new indirect enzyme immunoassay (EIA), Gonozyme (Abbott Laboratories), was assessed for rapid detection of gonococcal antigens. A correlation of optic density (OD) readings by EIA with colony counts of serial dilutions of Neisseria gonorrhoeae ATCC 19424 disclosed that EIA detected 10(3) CFU/ml at OD readings of 0.1 to 0.3, that EIA consistently detected greater than or equal to 10(4) CFU/ml at OD readings of 0.6 to 1.3, and that concentrations of greater than or equal to 10(5) CFU/ml were associated with OD readings of greater than or equal to 2.0. The clinical usefulness of Gonozyme was evaluated by comparing results of EIA with those of Gram stain (GS) and culture for N. gonorrhoeae from urethral and endocervical swabs obtained prospectively in 886 randomly selected patients attending a clinic for sexually transmitted diseases. The patients evaluated included 83 female contacts of men with gonorrhea and 56 patients seen at the clinic for test of cure. In tests with 295 males, the sensitivities of GS and EIA were 91.3 and 97.1%, respectively, and both tests had specificities of greater than 96%. In tests with 591 females, the sensitivities of GS and EIA were 51.4 and 96.4%, respectively (P less than 0.0001, Z proportionality test), and the specificities were 98.7 and 86.5%, respectively (P less than 0.0001). In tests with 61 females and 3 males, EIA was positive, whereas GS and cultures were negative for N. gonorrhoeae. Gonozyme is a highly sensitive method for rapid detection of gonococcal antigens. EIA is comparable to GS for males and more sensitive though less specific than GS for females. Possible reasons for the lower specificity of EIA for females are discussed. Due to its high negative predictive value for female contacts, EIA offers an alternative to epidemiological treatment of contacts before culture results.

Modified enzyme immunoassay for detecting Neisseria gonorrhoeae antigens

A commercial modification of an enzyme immunoassay (EIA) (Gonozyme; Abbott Laboratories, North Chicago, Ill.) for detection of Neisseria gonorrhoeae antigens was compared with conventional culturing. Specimens from males and females were collected at a sexually transmitted disease clinic; additional female specimens were collected at an obstetrics and gynecology clinic. EIA sensitivity and specificity for males were 100 and 98.6%, respectively (68 negative, 34 positive, 1 false-positive, and 0 false-negative). EIA sensitivity and specificity for female sexually transmitted disease clinic patients were 74.4 and 95.7%, respectively (66 negative, 29 positive, 3 false-positive, and 10 false-negative) EIA sensitivity and specificity for obstetrics and gynecology clinic patients were 100 and 99.2%, respectively (6 positive, 119 negative, 1 false-positive, and 0 false-negative). In female patients from whom multiple swab specimens were collected, the sequence of specimen collection and subsequent EIA analysis affected sensitivity.

Efficacy of an enzyme immunoassay with uncentrifuged first-voided urine for detection of gonorrhea in males

An enzyme immunoassay (Gonozyme; Abbott Laboratories, North Chicago, Ill.) for detection of Neisseria gonorrhoeae antigens was used to screen 184 urethral or uncentrifuged first-voided urine or both specimens from males and 78 cervical specimens. When compared with culture, the sensitivity and specificity of Gonozyme for cervical and urethral specimens were comparable to those in published reports. The sensitivity and specificity for urine specimens were 91.6 and 97.9%, respectively.