An evaluation of a novel dual treponemal/nontreponemal point-of-care test for syphilis as a tool to distinguish active from past treated infection.

BACKGROUND: Most syphilis point-of-care (POC) tests detect treponemal antibodies, which persist after successful treatment. Subsequent POC tests are positive, despite no active infection, and can lead to unnecessary treatment. We evaluated a new POC test, incorporating a nontreponemal component, to distinguish active from past infection. METHODS: Sera stored at 2 Australian laboratories were tested with DPP Screen and Confirm Assay. Treponemal and nontreponemal test lines were compared to corresponding conventional treponemal and nontreponemal reference test results: immunoassays and rapid plasma reagin (RPR), respectively, with RPR quantification by endpoint titration. POC test outcome concordance with conventional test results was assessed according to serological and clinical categories. RESULTS: Among 1005 serum samples tested, DPP treponemal line sensitivity was 89.8% (95% confidence interval [CI], 87.3%-91.9%) and specificity was 99.3% (95% CI, 97.0%-99.9%). DPP nontreponemal line sensitivity was 94.2% (95% CI, 91.8%-96.0%) and specificity was 62.2% (95% CI, 57.5%-66.6%). DPP test outcome (pair of test lines) was concordant with both reference test results for 94.3% of 404 high-titer infections, 90.1% of 121 low-titer infections, 27.5% of 211 past/treated infections, and 78.1% of 242 infections classified as not syphilis. Among 211 past/treated infections, 49.8% were incorrectly identified as active infection and a further 22.8% as not syphilis. CONCLUSIONS: DPP test use would result in identification of >93% of active syphilis infections, whereas just over half of past infections would be diagnosed as past or not syphilis, avoiding unnecessary treatment compared with other POC tests. This may be at the expense of missing some active infections; thus, its potential benefits will depend on the prevalence of past vs active infection in a population.

Prolonged second diagnostic window for human immunodeficiency virus type 1 in a fourth-generation immunoassay: are alternative testing strategies required?

Diagnosis of acute HIV is done by patient history and examination and testing of RNA, proviral DNA, and serology using fourth-generation antigen/antibody detection assays. We describe an HIV-1 primary infection with a second diagnostic window of 18 to 34 days on a fourth-generation immunoassay, which would have been missed using some current algorithms. Caution must be exercised when fourth-generation HIV-1 immunoassays are interpreted in isolation, and additional testing should be considered depending on patient risk assessment.

Significance of isolated reactive treponemal chemiluminescence immunoassay results.

BACKGROUND: Isolated reactive serum treponemal chemiluminescence immunoassay (CIA) specimens cause clinical uncertainty. METHODS: Sera were screened by CIA, and reactive samples underwent reflex testing with rapid plasma reagin (RPR), Treponema pallidum particle agglutination (TPPA), and fluorescent treponemal antibody absorption (FTA Abs) assays. Samples reactive only on the CIA were deemed "isolated" reactive CIA samples. We undertook detailed review of a subset of subjects with isolated reactive CIA specimens. RESULTS: Of 28 261 specimens, 1171 (4.1%) were reactive on CIA, of which 133 (11.3%) had isolated CIA reactivity. Most subjects (66 of 82 [80.5%]) with isolated reactive CIA specimens were from high-prevalence populations. We found evidence of CIA, TPPA, and FTA Abs seroreversion. The median chemiluminescent signal-to-cutoff ratio was similar for isolated reactive CIA sera and sera that were reactive on either FTA Abs or TPPA assays (2.19 vs 2.32; P = .15) but lower than for sera reactive on both FTA Abs and TPPA assays (12.37; P < .001) or for sera reactive on RPR assays (25.53; P < .001). A total of 11 of 20 patients (55%) with an isolated reactive CIA specimen who underwent medical record review had previous or subsequent evidence of syphilis infection. CONCLUSIONS: Isolated reactive CIA specimens may represent true T. pallidum infection and may be found after seroreversion of traditional treponemal assays.

Improving diagnosis of primary cytomegalovirus infection in pregnant women using immunoblots.

Human cytomegalovirus (CMV) is the most common infectious cause of mental disability in newborns of developed countries. Transmission of CMV from mother to baby is more frequent in maternal primary infection, although CMV reactivation causes more congenital infections overall. Current diagnostic tests for distinguishing primary and reactivation CMV have problems with interpretation and immunoblots may assist with diagnosis. Sera from 60 pregnant women were analyzed using conventional serology in parallel with a commercial immunoblot assay (using Recomblot, Mikrogen Diagnostik). Comparison of detection of CMV IgG, IgM, IgG avidity in maternal primary infection showed the immunoblot relative to conventional serology had sensitivity and specificity of 100% for IgG identification. The detection of IgM on immunoblot showed sensitivity of 75%, specificity of 62.5%, positive predictive value (PPV) of 81.8% and negative predictive value (NPV) of 52.6%. The immunoblot IgG avidity assay had sensitivity of 94.1%, with a PPV of 100% when identifying low avidity serum samples, and sensitivity of 100% with a PPV of 97.1% for high avidity serum samples. Overall agreement between conventional serology (IgM, IgG avidity) and immunoblot (IgM, IgG avidity) for detection of primary CMV infection was 65%. Although the immunoblot is effective in detecting IgG and determining IgG avidity, it showed no significant benefits in performance or utility as a first line diagnostic technique for IgM or primary CMV infection in pregnant women.

Positive Epstein-Barr virus and cytomegalovirus IgM assays in primary HIV infection.

We report three cases with misleading cytomegalovirus (CMV) or Epstein-Barr virus (EBV) immunoglobulin M (IgM) results during primary human immunodeficiency virus (HIV) infection. We determined the rate of positive anti-CMV IgM assays or anti-EBV capsid antigen IgM assays in sera from a group of well-characterized subjects with primary HIV infection as 2.9% (1/35; 95%CI: 0.15-16.6%) for each infection. The rate of positive anti-EBV capsid antigen IgM assays in subjects with positive hepatitis A virus IgM assays was 30% (6/20; 95%CI: 14.6-51.9%). Clinicians need to consider the limitations of IgM assays for diagnosis of herpesvirus infections, and consider testing for other infections with overlapping clinical manifestations.

Congenital cytomegalovirus--time to diagnosis, management and clinical sequelae in Australia: opportunities for earlier identification.

OBJECTIVES: To report on the burden of disease in Australian infants with congenital cytomegalovirus (cCMV) infection in the era of neonatal hearing screening and improved diagnostic techniques. DESIGN, SETTING AND PARTICIPANTS: National data were collected from across Australia via the Australian Paediatric Surveillance Unit (APSU) with monthly reporting by > 1000 clinicians between January 1999 and February 2009. For each reported case, data on investigations and epidemiological and clinical features were analysed. Detailed clinical reviews were performed on 42 infants in two Sydney tertiary paediatric infectious diseases clinics. RESULTS: There were 195 infants with cCMV identified, including 126 definite and 69 probable cases. Of these, 175 (90%) were symptomatic and only 15 were treated with antiviral agents. Identification was delayed beyond 60 days of age in 30 cases (15%). During the period of study, neonatal hearing screening was introduced for most Australian infants. Detection of hearing loss increased from 19% of cCMV cases in 1999-2003 to 31% in 2004-2009. Of 42 infants whose cases were reviewed in detail, 33 (79%) had symptomatic disease. DNA detection of CMV, using polymerase chain reaction testing of newborn screening cards, was useful in retrospective identification, and was strongly correlated with the presence of clinical sequelae (15/18; 83%). CONCLUSIONS: Congenital CMV is underdiagnosed, infrequently treated, and often manifests as isolated hearing loss. Delayed diagnoses both before and after the introduction of neonatal hearing screening represent missed treatment and management opportunities and are likely to lead to poorer, life-long outcomes for these children. Retrospective analysis of newborn screening cards for CMV should be undertaken for infants with sensorineural hearing loss, to identify unrecognised cCMV.

Enhanced serological diagnosis of invasive meningococcal disease by determining anti-group C capsule IgM antibody by enzyme immunoassay.

AIMS: To describe the development and evaluation of a diagnostic enzyme immunoassay (EIA) for IgM antibody to serogroup C capsular polysaccharide of Neisseria meningitidis (CCPS). METHODS: Purified CCPS was used as the antigen. The optical densities (OD) that determined the cut-off values for the assay were derived using sera from blood bank donors, and the accuracy was evaluated with sera from patients with culture-confirmed serogroup C and non-serogroup C invasive meningococcal disease (IMD), other infectious diseases, culture-confirmed pharyngeal carriage of N. meningitidis and immunoproliferative disorders. RESULTS: In sera collected between days 5 and 20 following positive culture, the assay had a sensitivity of 92%. The two negative sera were from a single patient but showed a significant rise in OD. The sensitivity declined to 80% on days 21-40 then to 75% on days 41-70. No positive reactions were detected in five samples collected after 71 days. The specificity of the assay was at least 97%. CONCLUSIONS: An EIA for IgM antibody to CCPS was evaluated for local conditions and had acceptable sensitivity and specificity. Use of the assay, based on a single blood sample, provided clinically and epidemiologically relevant information for individual and public health management of IMD.

Concurrent summer influenza and pertussis outbreaks in a nursing home in Sydney, Australia.

OBJECTIVE: To report on the investigation of a summer outbreak of acute respiratory illness among residents of a Sydney nursing home. DESIGN: An epidemiologic and microbiological investigation of the resident cohort at the time of the outbreak and medical record review 5 months later. SETTING: A nursing home located in Sydney, Australia, during February to July 1999. PATIENTS: The cohort of residents present in the nursing home at the time of the outbreak. INTERVENTIONS: Public health interventions included recommendations regarding hygiene, cohorting of residents and staff, closure to further admissions, and prompt reporting of illness; and virologic and serologic studies of residents. RESULTS: Of the 69 residents (mean age, 85.1 years), 35 fulfilled the case definition of acute respiratory illness. Influenza A infection was confirmed in 19 residents, and phylogenetic analysis of the resulting isolate, designated H3N2 A/Sydney/203/99, showed that it differed from strains isolated in eastern Australia during the same period. Serologic evidence of Bordetella infection was also found in 10 residents; however, stratified epidemiologic analysis pointed to influenza A as the cause of illness. CONCLUSIONS: The investigation revealed an unusual summer outbreak of influenza A concurrent with subclinical pertussis infection. Surveillance of acute respiratory illness in nursing homes throughout the year, rather than solely during epidemic periods, in combination with appropriate public health laboratory support, would allow initiation of a timely public health response to outbreaks of acute respiratory illness in this setting.

A laboratory-based evaluation of four rapid point-of-care tests for syphilis.

BACKGROUND: Syphilis point-of-care tests may reduce morbidity and ongoing transmission by increasing the proportion of people rapidly treated. Syphilis stage and co-infection with HIV may influence test performance. We evaluated four commercially available syphilis point-of-care devices in a head-to-head comparison using sera from laboratories in Australia. METHODS: Point-of-care tests were evaluated using sera stored at Sydney and Melbourne laboratories. Sensitivity and specificity were calculated by standard methods, comparing point-of-care results to treponemal immunoassay (IA) reference test results. Additional analyses by clinical syphilis stage, HIV status, and non-treponemal antibody titre were performed. Non-overlapping 95% confidence intervals (CI) were considered statistically significant differences in estimates. RESULTS: In total 1203 specimens were tested (736 IA-reactive, 467 IA-nonreactive). Point-of-care test sensitivities were: Determine 97.3%(95%CI:95.8-98.3), Onsite 92.5%(90.3-94.3), DPP 89.8%(87.3-91.9) and Bioline 87.8%(85.1-90.0). Specificities were: Determine 96.4%(94.1-97.8), Onsite 92.5%(90.3-94.3), DPP 98.3%(96.5-99.2), and Bioline 98.5%(96.8-99.3). Sensitivity of the Determine test was 100% for primary and 100% for secondary syphilis. The three other tests had reduced sensitivity among primary (80.4-90.2%) compared to secondary syphilis (94.3-98.6%). No significant differences in sensitivity were observed by HIV status. Test sensitivities were significantly higher among high-RPR titre (RPR ≥ 8) (range: 94.6-99.5%) than RPR non-reactive infections (range: 76.3-92.9%). CONCLUSIONS: The Determine test had the highest sensitivity overall. All tests were most sensitive among high-RPR titre infections. Point-of-care tests have a role in syphilis control programs however in developed countries with established laboratory infrastructures, the lower sensitivities of some tests observed in primary syphilis suggest these would need to be supplemented with additional tests among populations where syphilis incidence is high to avoid missing early syphilis cases.

The reliability of HBV core antibody in serological screening for hepatitis B virus.

INTRODUCTION: Accurate diagnosis of hepatitis B virus (HBV) infection is essential for infection control, treatment and screening of potential blood, organ and tissue donors. We assessed the sensitivity of the HBsAg and HBcAb as screening assays alone and in combination for detecting HBV infection in a series of Australian patients. The performance of the Architect (Abbott Diagnostics, Germany) and the Elecsys (Roche Diagnostics, Germany) platforms were assessed for detection of HBcAb. METHODS: There were 2778 blood samples assessed using the COBAS Ampliprep/TaqMan test for HBV DNA, of which 331 sera had concurrent HBV serology testing. This allowed determination of the correlation between HBV DNA and different serological markers. Of the 331 sera, 260 had sufficient residual volume to be retested for HBcAb using both Elecsys and the Architect assays. RESULTS: Of the 331 patients, one (0.3%) was negative by the Architect Anti-HBc II assay, in the presence of HBV DNA and positive HBsAg, consistent with recent infection. Positive HBcAb in the absence of HBV DNA was found in 67 of 331 (20.2%) patients. Of these, 18 of 67 had isolated HBcAb with negative results on all other tests, with 12 of 18 (3.6%) demonstrating low HBcAb signals on chemiluminscent microparticle assay. No cases of detectable HBV DNA in the presence of negative serology were found. When the HBcAb was used as a marker for past exposure or chronic HBV infection, the Architect Anti-HBc II assay demonstrated sensitivity and specificity of 98% and 79.9%, respectively, compared to 90% and 78.9%, respectively, for the Elecsys Anti-HBc assay. The combination of the Architect Anti-HBc II and HBsAg assays, as per conventional solid organ donor and recipient screening protocols, had 90% specificity and 100% sensitivity for determining HBV infection. CONCLUSION: This study shows that the use of combined HBsAg and HBcAb is sensitive and reliable for screening and predicting HBV nucleic acid test (NAT) positivity, whereas HBcAb alone missed an acute infection in this study population. There were no significant differences detectable between the Architect and the Elecsys HBcAb assays (p=0.001), suggesting laboratories should assess individual assays in the local population before use as screening tests.

Case report and evaluation of the frequency of the prozone phenomenon in syphilis serology - an infrequent but important laboratory phenomenon.

BACKGROUND: Treponema pallidum specific serology generally remains reactive for life. Therefore, the diagnosis of syphilis reinfection relies on clinical assessment and nontreponemal (reagin) serologic testing. The prozone phenomenon can lead to a falsely nonreactive rapid plasma reagin (RPR) assay result. METHODS: We report a case of secondary syphilis in a HIV infected patient with a previous history of syphilis infection, where a falsely nonreactive RPR assay was associated with a delayed diagnosis of reinfection and infectious syphilis. The prozone phenomenon was detected in several of the patient's serum samples collected around this time. We subsequently undertook a prospective evaluation for the prozone phenomenon in 3222 consecutive sera, which were assayed using the RPR assay for clinical purposes over a 10-month period. RESULTS: The overall rate of the prozone phenomenon was 2 out of 3222 samples (0.06%; 95% confidence interval (CI): 0.02-0.22%) and the rate per reactive sample was 2 out of 397 (0.5%; 95% CI: 0.14-1.81%). CONCLUSION: Clinicians should request RPR testing at dilutions of sera when syphilis is suspected clinically and the RPR assay is nonreactive.

Post-streptococcal glomerulonephritis in Sydney: a 16-year retrospective review.

AIM: Post-streptococcal glomerulonephritis (PSGN) is a frequent cause of acute nephritis in children. Numerous studies have described PSGN in high-risk populations yet few data describing PSGN in a low-incidence population exist. This study aimed to describe the epidemiology, clinical manifestations, diagnosis, complications and outcomes of PSGN in an urban Australian population. METHODS: A 16-year retrospective review of case notes and laboratory data was conducted at a tertiary Sydney paediatric hospital. RESULTS: Thirty-seven children were treated for PSGN with a mean age of 8.1 years (range 2.6-14.1 years). Twenty-eight subjects (75.7%) had a history of a recent upper respiratory tract or skin infection. Hypertension and/or oedema was present in 29 subjects (78.4%). Streptococcal pharyngitis was identified as the likely source in 17 subjects (45.9%). Skin infections occurred less frequently. Antibodies against streptolysin O, streptokinase or deoxyribonuclease B were elevated when a single titre was measured in 35 subjects (94.6%). Thirty subjects (81.1%) developed renal impairment (median peak creatinine, 95 micromol/L, range 39-880 micromol/L). No correlation was demonstrated between peak creatinine, age, ethnicity, streptococcal titres and serum complement levels. The mean length of admission was 8.2 days. Seven subjects (18.9%) had a complicated course with three subjects requiring dialysis. Only one subject has ongoing renal dysfunction. CONCLUSION: Significant differences are seen in a low-incidence urban Australian population with PSGN when compared with endemic or epidemic disease in high-risk populations. The higher rates of complications that were seen compared with previously studied populations need further clarification.

Pox in the docks: varicella outbreak in an Australian prison system.

OBJECTIVES: 1. Describe an outbreak of varicella in a prison system. 2. Highlight the risks of disease transmission within the prison environment. 3. Promote infection control guidelines for high-risk sub-groups within the prison system, including the application of quarantine. SETTING: Four prisons, one prison hospital, the prison transport system, one courthouse. MAIN OUTCOME MEASURES: Number of cases of varicella infection; reported varicella immunity status of cases and contacts; immunity status of known HIV antibody positive inmates. RESULTS: Five cases of chickenpox were identified. There were 23 contacts of the Index Case occurring during transport between prison and court and whilst being held in the court holding cells. Two of these contacts developed chickenpox despite having given a prior history of infection. There were over 300 inmates exposed to varicella zoster virus (VZV) during the outbreak, including one HIV antibody positive inmate who had serologically confirmed immunity. This inmate developed shingles following exposure to VZV from one of the cases. CONCLUSIONS: There is an elevated risk of respiratory transmission of infections such as chickenpox in prisons. Clear guidelines should be in place to protect HIV antibody positive people, pregnant women, and others who are at increased risk of complications from such infections. In the case of varicella, all inmates and staff without documented immunity should be screened to determine immunity, and if non-immune, should be offered VZV vaccination. Every effort should be made to prevent HIV antibody positive inmates being exposed to varicella, regardless of their varicella immunity status. If an HIV antibody positive inmate, who is known to be non-immune is exposed to varicella, Varicella Zoster immunoglobulin should be given within 96 h.