Detection of SARS-CoV-2 IgG Targeting Nucleocapsid or Spike Protein by Four High-Throughput Immunoassays Authorized for Emergency Use.

A total of 1,200 serum samples that were tested for SARS-CoV-2 IgG antibody using the Abbott Architect immunoassay targeting the nucleocapsid protein were run in 3 SARS-CoV-2 IgG immunoassays targeting spike proteins (DiaSorin Liaison, Ortho Vitros, and Euroimmun). Consensus-positive and consensus-negative interpretations were defined as qualitative agreement in at least 3 of the 4 assays. Agreement of the 4 individual assays with a consensus-negative interpretation (n = 610) ranged from 96.7% to 100%, and agreement with a consensus-positive interpretation (n = 584) ranged from 94.3% to 100%. Laboratory-developed inhibition assays were utilized to evaluate 49 consensus-negative samples that were positive in only one assay; true-positive reactivity was confirmed in only 2 of these 49 (4%) samples. These findings demonstrate very high levels of agreement among 4 SARS-CoV-2 IgG assays authorized for emergency use, regardless of antigen target or assay format. Although false-positive reactivity was identified, its occurrence was rare (no more than 1.7% of samples for a given assay).

A kidney transplant recipient with renal medullary viral cytopathic changes.

We present a case of JC polyomavirus (JCV)-associated nephropathy (PyVAN) in an asymptomatic deceased-donor kidney transplant recipient. Despite the presence of viral cytopathic effect in the kidney biopsy and positive BK polyomavirus (BKV) in situ hybridization (ISH), BKV real-time polymerase chain reaction (PCR) results of plasma and urine were negative. JCV ISH was performed and was found to be positive. JCV real-time PCR on urine, plasma, and the kidney biopsy tissue was positive. Reduction in immunosuppression resulted in resolution of JCV viremia. This case highlights that JC-PyVAN is a distinct clinical entity and is likely to have a better clinical outcome than BK-PyVAN. Concurrent infection with BKV and JCV may occur, but may be difficult to confirm due to the potential for cross-reactivity between BKV and JCV ISH stains.

Relationship between DiaSorin Liaison Treponema pallidum antibody indices and confirmatory assay results in the reverse syphilis testing algorithm.

Published studies show that >99% of sera reactive in the reverse syphilis testing algorithm (RSTA) screening assay with an index above an assay-specific threshold confirm as reactive, with either a rapid plasma reagin-reactive (RPRR) or RPR-nonreactive/Treponema pallidum particle agglutination-reactive (TPPAR) result. However, the relationship between screen indices and confirmatory patterns has not been characterized. We thus assessed confirmatory testing results for 577 sera submitted for RSTA testing and a screen-reactive result in the DiaSorin Liaison assay. The median screen index was significantly higher for RPRR samples than TPPAR samples (55.6 versus 10.4), and the proportion with indices >28.3 (median for all 577 samples) was significantly higher for RPRR versus TPPAR samples (82% versus 26%). However, RPRR titers did not significantly correlate with screen indices (R2 = 0.02). These findings demonstrate a significant relationship between RSTA screen indices and confirmatory assay results. The clinical utility of this relationship requires further study.

Relationship between hepatitis C virus (HCV) IgG index values and quantitative HCV RNA results in HCV IgG-reactive serum samples.

Centers for Disease Control guidelines recommend hepatitis C virus (HCV) RNA testing of all HCV IgG-reactive samples, although earlier studies found that IgG-reactive samples with low indices were negative in qualitative RNA assays. To determine if previous study results could be confirmed using current real-time RT-PCR technology, we investigated the relationship between HCV IgG index (Ortho VITROS) and quantitative HCV RNA results (cobas HCV) for 2368 consecutive IgG-reactive sera. Results were segregated into Low (1.00-16.0), Medium (16.1-30.0), and High (>30.0) IgG index groups. Although median viral load (VL) of RNA-positive samples was similar in all 3 groups, the percentage with low VL (1.18-4.16 log IU/mL) was increased for the Low group. Further analysis of the Low group revealed that 23 of 370 (6%) samples with IgG indices ≤8.00 were RNA-positive, and 13/23 (57%) had low VL. Our analysis supports the Centers for Disease Control recommendation to test all HCV IgG-reactive sera for HCV RNA.

Herpes simplex virus type 2 (HSV-2) IgG index values in two immunoassays in relation to HSV-2 IgG inhibition assay results.

CDC guidelines recommend confirmatory testing of sera with low-positive indices (1.10-3.50) in the HerpeSelect® (HSLT) HSV-2 IgG screening assay. To determine if this recommendation is adequate for our patient population, we reviewed HSLT HSV-2 IgG screening indices for 262 screen-positive sera (index >1.10) tested in our confirmatory assay, which assesses inhibition of binding to recombinant gG2 by HSV-1- and HSV-2-infected cell lysates. To determine how the recommendation affects other screening assays, we tested these samples in the Liaison® HSV-2 IgG assay. Of 124 false-positive sera, 20% and 39% had an index >3.50 in the HSLT and Liaison screening assays, respectively. In both assays, 51% of 63 indeterminate sera (inhibition by HSV-1 lysate) had indices >3.50. Similarly, ≥75% of 75 true-positive samples exhibited indices >3.50 in both assays. Thus, confirmatory testing only of sera with low-positive HSV-2 IgG indices misses some false-positive and indeterminate samples, leading to misdiagnosis of HSV-2 infection.

A summary of meeting proceedings on addressing variability around the cut point in serial interferon-γ release assay testing.

On June 13, 2012, a group of key stakeholders, leaders, and national experts on tuberculosis (TB), occupational health, and laboratory science met in Atlanta, Georgia, to focus national discussion on the higher than expected positive results occurring among low-risk, unexposed healthcare workers undergoing serial testing with interferon-γ release assays (IGRAs). The objectives of the meeting were to present the latest clinical and operational research findings on the topic, to discuss evaluation and treatment algorithms that are emerging in the absence of national guidance, and to develop a consensus on the action steps needed to assist programs and physicians in the interpretation of serial testing IGRA results. This report summarizes its proceedings.

Identification of acid-fast bacilli using pyrosequencing analysis.

Pyrosequence identification of 117 isolates of acid-fast bacilli (AFB) was compared to both routine phenotypic methods and Sanger sequencing. Two (2) vendor-provided pyrosequencing primers specific for AFB were used for the study. Pyrosequence analysis correctly identified 114 (98%) of the tested 117 AFB isolates. Among the test Mycobacterium spp., 18 of 20 Mycobacterium spp. were identified correctly to the species level. All rapidly growing mycobacteria were correctly identified to species by pyrosequencing. Other slowly growing mycobacteria such as Mycobacterium tuberculosis, Mycobacterium kansasii, Mycobacterium avium-intracellulare, and others were easily identified by pyrosequencing. Only Mycobacterium simiae and Mycobacterium scrofulaceum were not identifiable by the pyrosequence method. Among the 25 Nocardia isolates, all were correctly identified to the genus level. Identification of AFB by pyrosequence analysis provides both a rapid and accurate method for this group of organisms.

Additional HIV-1 mutation patterns associated with reduced phenotypic susceptibility to etravirine in clinical samples.

We investigated the phenotypic impact of a number of uncommon amino acid substitutions at HIV-1 reverse transcriptase positions 103 and 138, which are not part of the etravirine resistance score and were found in combination with the high-impact mutation K101P. Etravirine phenotypic fold changes were 380-1400 for K101P + E138A/G/Q + K103N/S/T + V179I and 12-130 for K101P + (K103S +/- V179I) in the absence of E138A/G/Q. Although the effect of K103S is unclear, additional position 138 substitutions seem important for etravirine susceptibility.