Theel, Elitza S.

ABSTRACTDetection ofCryptococcusantigen (CrAg) is invaluable for establishing cryptococcal disease. Multiple different methods for CrAg detection are available, including a lateral flow assay (LFA). Despite excellent performance of the CrAg LFA, we have observed multiple cases of low-titer (≤1:5) positive CrAg LFA results in patients for whom cryptococcosis was ultimately excluded. To investigate the accuracy of low-titer positive CrAg LFA results, we performed chart reviews for all patients with positive CrAg LFA results between June 2014 and December 2016. During this period, serum and/or cerebrospinal fluid (CSF) samples from 3,969 patients were tested with the CrAg LFA, and 55 patients (1.5%) tested positive. Thirty-eight of those patients lacked a history of cryptococcal disease and were the focus of this study. Fungal culture or histopathology confirmedCryptococcusinfection for 20 patients (52.6%), and CrAg LFA titers in serum and CSF samples ranged from 1:5 to ≥1:2,560. For the 18 patients (47.4%) without culture or histopathological confirmation, the CrAg LFA results were considered true-positive results for 5 patients (titer range, 1:10 to ≥1:2,560), due to clinical improvement with targeted therapy and decreasing CrAg LFA titers. The remaining 13 patients had CrAg LFA titers of 1:2 (n= 11) or 1:5 (n= 2) and were ultimately diagnosed with an alternative condition (n= 11) or began therapy for possible cryptococcosis without improvement (n= 2), leading to an overall CrAg LFA false-positive rate of 34%. We recommend careful clinical correlation prior to establishing a diagnosis of cryptococcal infection for patients with first-time positive CrAg LFA titers of 1:2.

ABSTRACT Serologic evaluation for Zika virus (ZIKV) infection currently includes an initial screen using an anti-ZIKV IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA) followed by supplemental testing of specimens with nonnegative results by a plaque reduction neutralization test (PRNT). We compared the performance characteristics of three ELISAs for the detection of IgM class antibodies to ZIKV, including the Centers for Disease Control and Prevention (CDC) Zika MAC-ELISA, the InBios ZIKV Detect MAC-ELISA, and the Euroimmun anti-Zika Virus IgM ELISA. Additionally, we present our initial experiences with ZIKV serologic testing from a national reference laboratory perspective. Using both retrospectively and prospectively collected specimens from patients with possible ZIKV infection, we show that the CDC and InBios MAC-ELISAs perform comparably to each other, with positive agreement, negative agreement, and interrater kappa values ranging from 87.5% to 93.1%, 95.7% to 98.5%, and 0.52 to 0.83, respectively. In contrast, comparison of the Euroimmun ZIKV ELISA to either the CDC or InBios MAC-ELISAs resulted in positive agreement, negative agreement, and interrater kappa values ranging from 17.9% to 42.9%, 91.7% to 98.6%, and 0.10 to 0.39, respectively. Among the 19 prospective samples submitted for PRNT, nine were negative, eight specimens had neutralizing antibodies to a flavivirus (unable to be identified), and one sample each was confirmed for ZIKV or dengue virus infection. This study highlights the ongoing challenges associated with serologic diagnosis of ZIKV infection. Although the availability of a commercial serologic test for ZIKV has greatly expanded the national capacity for such testing, the need to further characterize and improve these assays, particularly with regard to specificity, remains.

ABSTRACT Parasites are an important cause of human disease worldwide. The clinical severity and outcome of parasitic disease is often dependent on the immune status of the host. Specific parasitic diseases discussed in this chapter are amebiasis, giardiasis, cryptosporidiosis, cyclosporiasis, cystoisosporiasis, microsporidosis, granulomatous amebic encephalitis, toxoplasmosis, leishmaniasis, Chagas disease, malaria, babesiosis, strongyloidiasis, and scabies.

ABSTRACT Lyme disease prevails as the most commonly transmitted tick-borne infection in the United States, and serologic evaluation for antibodies to Borrelia burgdorferi remains the recommended modality for diagnosis. This review presents a brief historical perspective on the evolution of serologic assays for Lyme disease and provides a summary of the performance characteristics for the currently recommended two-tiered testing algorithm (TTTA). Additionally, a recently proposed alternative to the traditional TTTA is discussed, and novel methodologies, including immuno-PCR and metabolic profiling for Lyme disease, are outlined.

ABSTRACT Detection of the Histoplasma capsulatum urinary antigen (UAg) is among the most sensitive and rapid means to diagnose histoplasmosis. Previously, we evaluated analyte-specific reagents (ASR) manufactured by IMMY (Norman, OK) for detection of Histoplasma galactomannan (GM) in urine using an enzyme immunoassay (EIA), and we showed low positive agreement (64.5%) with the MiraVista (MVista) Histoplasma antigen (Ag) quantitative EIA (MiraVista Diagnostics, Indianapolis, IN). Here we reevaluated the IMMY GM ASR following modification of our original assay protocol and introduction of an indeterminate range. A total of 150 prospectively collected urine samples were tested with both the IMMY and MVista EIAs, and clinical histories were recorded for all study subjects. The IMMY GM ASR showed positive and negative agreements of 82.3% (14/17 samples) and 100% (121/121 samples), respectively (with exclusion of 12 indeterminate results), and overall agreement of 90% (135/150 samples) with respect to the MVista EIA. Of the three patients with negative IMMY GM ASR results and positive MVista EIA results, testing was performed for initial diagnostic purposes for one patient (<0.4 ng/ml by the MVista EIA) and UAg levels were being monitored for the remaining two patients (both <0.7 ng/ml by the MVista EIA). The MVista EIA results were positive for 6/12 samples that tested indeterminate by the IMMY GM ASR. We also show that the IMMY GM ASR can be used to serially monitor Histoplasma UAg levels. In conclusion, we demonstrate that, with modification, the IMMY GM ASR is a reliable rapid assay for detection of Histoplasma UAg.

ABSTRACT We surveyed national Helicobacter pylori diagnostic testing practices and diagnoses using commercial and Medicare medical claims data from Optum Labs (Cambridge, MA). Serologic testing for antibodies to H. pylori remains the most commonly ordered diagnostic test despite recent expert recommendations. Changes in reimbursement for serologic testing will likely drive future provider ordering practices.

Despite preexisting cytomegalovirus (CMV) immunity, CMV‐seropositive liver transplantation (LT) patients remain at risk of CMV infection. We hypothesized that the pre‐transplant CMV antibody titer correlates with the risk of CMV reactivation. We conducted a retrospective study of CMV‐seropositive LT recipients who did not receive anti‐CMV prophylaxis from 2007 to 2013. The pre‐transplant CMV immunoglobulin G (IgG) titer, which was measured with an enzyme‐linked fluorescent immunoassay, was assessed as a risk factor for CMV reactivation with multivariate Cox proportional hazards models. The population consisted of 225 CMV‐seropositive LT patients with a median age of 57 years (interquartile range, 47‐62 years). The CMV titer distributions were as follows: <60 (40%) and ≥60 AU/mL (60%). The Kaplan‐Meier estimates for CMV infection were 17% at 3 months, 18% at 6 months, and 19% at 12 months after transplantation. In a univariate analysis, a marginally significant increased risk of CMV infection was seen in LT recipients with a pre‐transplant CMV IgG titer < 60 AU/mL versus ≥ 60 AU/mL [hazard ratio (HR), 1.79; 95% confidence interval (CI), 0.98‐3.28 (P =0.06)]. This risk was statistically significant in the subgroup of recipients who received allografts from CMV‐seropositive donors [HR, 2.21; 95% CI, 1.15‐4.26 (P =0.02)]. In a multivariate analysis, a pre‐transplant CMV IgG titer < 60 AU/mL was significantly associated with CMV infection [HR, 3.11; 95% CI, 1.60‐6.03 (P < 0.001)]. The other risk factors were high body mass index, donor CMV seropositivity, prolonged cold ischemic time, use of an interleukin‐2 receptor antagonist for induction therapy, and high numbers of post‐transplant infections. A lower pre‐transplant CMV antibody titer is significantly associated with CMV infection after LT. Quantitative measurement of CMV‐specific humoral immunity may have a potential role in improving the CMV prevention strategy in CMV‐seropositive LT recipients.Liver Transpl 21:539–546, 2015. © 2015 AASLD.