Diagnosing fungal infections in clinical practice: a narrative review.

BACKGROUND: Invasive fungal infections (IFI) present a major medical challenge, with an estimated 6.5 million cases annually, resulting in 3.8 million deaths. Pathogens such as Aspergillus spp. Candida spp. Mucorales spp. Cryptococcus spp. and other fungi species contribute to these infections, posing risks to immunocompromised individuals. Early and accurate diagnosis is crucial for effective treatment and better patient outcomes. AREAS COVERED: This narrative review provides an overview of the current methods and challenges associated with diagnosing fungal diseases, including invasive aspergillosis and invasive candidiasis, as well as rare and endemic fungal infections. Various diagnostic techniques, including microscopy, culture, molecular diagnostics, and serological tests, are reviewed, highlighting their respective advantages and limitations and role in clinical guidelines. To illustrate, the need for improved diagnostic strategies to overcome existing challenges, such as the low sensitivity and specificity of current tests and the time-consuming nature of traditional culture-based methods, is addressed. EXPERT OPINION: Current advancements in fungal infection diagnostics have significant implications for healthcare outcomes. Improved strategies like molecular testing and antigen detection promise early detection of fungal pathogens, enhancing patient management. Challenges include global access to advanced technologies and the need for standardized, user-friendly point-of-care diagnostics to improve diagnosis of fungal infections globally.

Performance of the clarus Aspergillus galactomannan enzyme immunoassay prototype for the diagnosis of invasive pulmonary aspergillosis in serum.

BACKGROUND: Serum galactomannan (GM) testing is essential for diagnosing invasive aspergillosis (IA), particularly in immunocompromised individuals. The global lack of on-site GM testing capacities necessitates cost-effective alternatives, such as .the clarus Aspergillus GM enzyme immunoassay prototype (clarus AGM prototype). METHODS: This single-centre, cross-sectional study compared the diagnostic performance of the clarus AGM prototype (IMMY, Norman, Oklahoma) with the serological gold standard (=Platelia AGM assay; Bio-Rad, Marnes-la-Cocquette, France). IA was classified according to modified 2020 EORTC/MSG consensus and 2024 FUNDICU criteria. In total, 300 prospectively (May-Dec 2023) and retrospectively (2012-2015) collected samples were included. RESULTS: Among 300 samples from 232 patients, 49 (16%) were classified as proven (n = 1) or probable IA (n = 48). In non-IA cases (n = 250), one patient was classified as possible IA. With the manufacturer recommended cut-off of ≥0.2, sensitivity and specificity of the clarus AGM prototype were 27% (13/49; 95% confidence interval [CI]: 15%-41%) and 99% (248/250; 95% CI: 97%-100%), respectively, while sensitivity and specificity were 78% and 79% when using the optimised Youden's cut-off of 0.0045 ODI. ROC curve analysis demonstrated an area under the curve (AUC) of 0.829 (95% CI: 0.760-0.898) for the clarus AGM prototype in distinguishing between proven/probable IA and non-IA. The AUC for the Platelia AGM was 0.951 (95% CI: 0.909-994). Spearman's correlation analysis showed a weak correlation between the two assays (0.382; p < .001). CONCLUSIONS: The weak correlation between the clarus AGM prototype and Platelia AGM highlights the need for further investigation into the clinical performance of the clarus AGM prototype, giving the different antigen epitopes addressed.

Antifungals in Patients With Extracorporeal Membrane Oxygenation: Clinical Implications.

Extracorporeal membrane oxygenation (ECMO) is a life-saving technique used in critical care medicine for patients with severe respiratory or cardiac failure. This review examines the treatment and prophylaxis of fungal infections in ECMO patients, proposing specific regimens based on available data for different antifungals (azoles, echinocandins, amphotericin B/liposomal amphotericin B) and invasive fungal infections. Currently, isavuconazole and posaconazole have the most supported data, while modified dosages of isavuconazole are recommended in ECMO. Echinocandins are preferred for invasive candidiasis. However, choosing echinocandins is challenging due to limited and varied data on concentration loss in the ECMO circuit. Caution is likewise advised when using liposomal amphotericin B due to uncertain concentrations and potential ECMO dysfunction based on scarce data. We further conclude with the importance of further research on the impact of ECMO on antifungal drug concentrations to optimize dosing regimens in critically ill patients.

Implementation of an antimicrobial stewardship program for urinary tract infections in long-term care facilities: a cluster-controlled intervention study.

BACKGROUND: Widespread inappropriate use of antimicrobial substances drives resistance development worldwide. In long-term care facilities (LTCF), antibiotics are among the most frequently prescribed medications. More than one third of antimicrobial agents prescribed in LTCFs are for urinary tract infections (UTI). We aimed to increase the number of appropriate antimicrobial treatments for UTIs in LTCFs using a multi-faceted antimicrobial stewardship intervention. METHODS: We performed a non-randomized cluster-controlled intervention study. Four LTCFs of the Geriatric Health Centers Graz were the intervention group, four LTCFs served as control group. The main components of the intervention were: voluntary continuing medical education for primary care physicians, distribution of a written guideline, implementation of the project homepage to distribute guidelines and videos and onsite training for nursing staff. Local nursing staff recorded data on UTI episodes in an online case report platform. Two blinded reviewers assessed whether treatments were adequate. RESULTS: 326 UTI episodes were recorded, 161 in the intervention group and 165 in the control group. During the intervention period, risk ratio for inadequate indication for treatment was 0.41 (95% CI 0.19-0.90), p = 0.025. In theintervention group, the proportion of adequate antibiotic choices increased from 42.1% in the pre-intervention period, to 45.9% during the intervention and to 51% in the post-intervention period (absolute increase of 8.9%). In the control group, the proportion was 36.4%, 33.3% and 33.3%, respectively. The numerical difference between intervention group and control group in the post-intervention period was 17.7% (difference did not reach statistical significance). There were no significant differences between the control group and intervention group in the safety outcomes (proportion of clinical failure, number of hospital admissions due to UTI and adverse events due to antimicrobial treatment). CONCLUSIONS: An antimicrobial stewardship program consisting of practice guidelines, local and web-based education for nursing staff and general practitioners resulted in a significant increase in adequate treatments (in terms of decision to treat the UTI) during the intervention period. However, this difference was not maintained in the post-intervention phase. Continued efforts to improve the quality of prescriptions further are necessary. TRIAL REGISTRATION: The trial was registered at ClinicalTrials.gov NCT04798365.

New treatment options for critically important WHO fungal priority pathogens.

BACKGROUND: Yet often overlooked in public health discourse, fungal infections pose a crucial global disease burden associated with annual mortality rates approximately equal to tuberculosis and HIV. In response, the WHO published its first global priority list of fungal pathogens in 2022 assigning Aspergillus fumigatus, Candida albicans, Candida auris, and Cryptococcus neoformans to the critical group. OBJECTIVES: This review provides succinct insights into novel antifungals in development, aiming to contribute valuable information and perspectives with a focus on recent clinical findings and new treatment approaches for critical members of the WHO fungal pathogen priority list. SOURCES: PubMed literature search using 'Aspergillus fumigatus', 'Cryptococcus neoformans', 'Candida auris', and 'Candida albicans', along with the names of novel antifungal substances, including 'fosmanogepix', 'ibrexafungerp', 'opelconazole', 'oteseconazole', 'MAT2203', 'olorofim', and 'rezafungin' was conducted. CONTENT: For each critical pathogen, current issues and global clinical data from recent trials are covered. The remarkable development of three new antifungal therapeutics recently receiving Food and Drug Administration approval (ibrexafungerp-June 2021, oteseconazole -April 2022, and rezafungin-March 2023) is outlined, with two more exciting new antifungal substances, namely, olorofim and fosmanogepix expecting approval within the next years. Ibrexafungerp, fosmanogepix, and rezafungin have additionally been granted orphan drug status by the European Medicines Agency in Europe (ibrexafungerp-November 2021, fosmanogepix-July 2022, and rezafungin-January 2024). IMPLICATIONS: Although the limited number of targets and the emergence of resistance have posed challenges to antifungal treatment, new drugs such as ibrexafungerp, rezafungin, fosmanogepix, or olorofim have shown promising clinical efficacy. These drugs not only provide alternative options for invasive fungal infections but also alleviate treatment in outpatient settings. More clinical data, implementation of stewardship programmes, and surveillance, including utilization of drugs in agriculture, are necessary to prevent resistance development and to ensure the safety and efficacy of these new agents.

Therapeutic drug monitoring of antifungal therapies: do we really need it and what are the best practices?

INTRODUCTION: Despite advancements, invasive fungal infections (IFI) still carry high mortality rates, often exceeding 30%. The challenges in diagnosis, coupled with limited effective antifungal options, make managing IFIs complex. Antifungal drugs are essential for IFI management, but their efficacy can be diminished by drug-drug interactions and pharmacokinetic variability. Therapeutic Drug Monitoring (TDM), especially in the context of triazole use, has emerged as a valuable strategy to optimize antifungal therapy. AREAS COVERED: This review provides current evidence regarding the potential benefits of TDM in IFI management. It discusses how TDM can enhance treatment response, safety, and address altered pharmacokinetics in specific patient populations. EXPERT OPINION: TDM plays a crucial role in achieving optimal therapeutic outcomes in IFI management, particularly for certain antifungal agents. Preclinical studies consistently show a link between therapeutic drug levels and antifungal efficacy. However, clinical research in mycology faces challenges due to patient heterogeneity and the diversity of fungal infections. TDM's potential advantages in guiding Echinocandin therapy for critically ill patients warrant further investigation. Additionally, for drugs like Posaconazole, assessing whether serum levels or alternative markers like saliva offer the best measure of efficacy is an intriguing question.

Early attainment of isavuconazole target concentration using an increased loading dose in critically ill patients with extracorporeal membrane oxygenation.

BACKGROUND: In critically ill patients with extracorporeal membrane oxygenation (ECMO) attainment of target concentration of isavuconazole is delayed using the routine loading dose. OBJECTIVES: We investigated the influence of increasing the first loading dose of isavuconazole on plasma concentrations in critically ill patients treated with ECMO. METHODS: Fifteen patients were included in this study, and isavuconazole concentrations were measured at several timepoints starting 2 h after the first isavuconazole dose up to 168 h. By interim analysis of isavuconazole concentrations and meticulous screening for adverse events, the first loading dose was stepwise increased from 200 to 300 mg, and finally to 400 mg. RESULTS: Seven of 15 patients (47%) received standard isavuconazole loading dosage with 200 mg as the first dose, 3/15 (20%) received 300 mg, and 5/15 (33%) received 400 mg isavuconazole as the first dose, followed by subsequent standard dosing in all patients. In patients receiving 400 mg as the first dose all isavuconazole concentrations were significantly higher at timepoints up to the first 24 h, resulting in higher proportions of isavuconazole concentrations ≥1 mg/L compared with patients with other loading dosages. In timepoints ≥24 h after isavuconazole initiation all patient groups reached comparable plasma concentrations, regardless of the first loading dose regimen. We did not observe concentrations above ≥5 mg/L or any adverse events related to isavuconazole administration. CONCLUSIONS: In critically ill patients with ECMO the 400 mg loading dose of isavuconazole resulted in immediate median isavuconazole plasma concentrations ≥1 mg/L and remained constant above this threshold after the first loading dose.

Human Tularemia Epididymo-Orchitis Caused by Francisella tularensis Subspecies holartica, Austria.

A previously healthy man in Austria had tularemia epididymo-orchitis develop, leading to unilateral orchiectomy. Francisella tularensis subspecies holartica was detected by 16S rRNA gene sequencing analysis of inflamed granulomatous testicular tissue. Clinicians should suspect F. tularensis as a rare etiologic microorganism in epididymo-orchitis patients with relevant risk factors.

Fungal translocation measured by serum 1,3-ß-D-glucan correlates with severity and outcome of liver cirrhosis-A pilot study.

BACKGROUND & AIMS: On a global scale, liver cirrhosis is attributable to ~1 million deaths per year. This systemic disease comes along with diverse sequelae, including microbiota alterations, increased gut permeability and translocation of microbial components into the systemic circulation. Alongside the extensively studied influence of bacterial translocation and its host-pathogen interactions, far less is known about the role and impact of fungal components once having crossed the intestinal barrier. METHODS: Including 70 patients with different aetiologies of liver cirrhosis, we investigated the relationship between fungal translocation, measured by 1,3-ß-D-glucan (BDG), and biomarkers of gut integrity, inflammation and severity/outcome of liver disease. RESULTS: Patients with cirrhosis Child-Pugh class (CPC)-B were more likely to have positive serum BDG (aOR 5.4, 95% CI 1.2-25.2) compared to patients with cirrhosis CPC-A. BDG showed a moderate positive correlation with several markers of inflammation (sCD206, sCD163, Interleukin 8, interferon-gamma-induced protein). Mortality differed significantly between patients with positive versus negative BDG (log-rank test, p = 0.015). The multivariable Cox regression model yielded an aHR of 6.8 (95% CI 1.8-26.3). DISCUSSION: We observed trends for increased fungal translocation depending on the severity of liver cirrhosis, an association of BDG with an inflammatory environment and the adverse effects of BDG on disease outcome. In order to gain more in-depth knowledge about (fungal-)dysbiosis and its detrimental consequences in the setting of liver cirrhosis, these trends need to be studied in more detail including prospective sequential testing in larger cohorts together with mycobiome analyses. This will further elucidate complex host-pathogen interactions and potentially introduce points of application for therapeutic interventions.

Preanalytical stability of SARS-CoV-2 anti-nucleocapsid antibodies.

OBJECTIVES: Anti-nucleocapsid (NC) antibodies are produced in response to SARS-CoV-2 infection. Therefore, they are well suited for the detection of a previous infection. Especially in the case of seroprevalence studies or during the evaluation of a novel in-vitro diagnostic test, samples have been stored at <-70 °C (short- and long-term) or 2-10 °C (short-term) before analysis. This study aimed to assess the impact of different storage conditions relevant to routine biobanking on anti-NC antibodies. METHODS: The preanalytical impact of short-term storage (84 [58-98] days) on <-70 °C and for 14 days at 2-10 °C was evaluated using samples from 111 donors of the MedUni Vienna Biobank. Long-term effects (443 [409-468] days) were assessed using 208 samples from Biobank Graz and 49 samples from Biobank Vienna. Anti-Nucleocapsid antibodies were measured employing electrochemiluminescence assays (Roche Anti-SARS-CoV-2). RESULTS: After short-term storage, the observed changes did not exceed the extent that could be explained by analytical variability. In contrast, results after long-term storage were approximately 20% higher and seemed to increase with storage duration. This effect was independent of the biobank from which the samples were obtained. Accordingly, the sensitivity increased from 92.6 to 95.3% (p=0.008). However, comparisons with data from Anti-Spike protein assays, where these deviations were not apparent, suggest that this deviation could also be explained by the analytical variability of the qualitative Anti-NC assay. CONCLUSIONS: Results from anti-NC antibodies are stable during short-term storage at <-70 °C and 2-10 °C. After long-term storage, a slight increase in sensitivity could not be ruled out.

Siderophores: a potential role as a diagnostic for invasive fungal disease.

PURPOSE OF REVIEW: Invasive fungal diseases (IFDs) such as invasive aspergillosis continue to be associated with high morbidity and mortality while presenting significant diagnostic challenges. Siderophores are high-affinity Fe 3+ chelators produced by Aspergillus spp. and other fungi capable of causing IFD. Previously evaluated as a treatment target in mucormycosis, siderophores have recently emerged as new diagnostic targets for invasive aspergillosis and scedosporiosis. Here, we review the diagnostic potential of siderophores for diagnosing IFD, with a particular focus on invasive aspergillosis. RECENT FINDINGS: The major secreted siderophore of A. fumigatus , triacetylfusarinine C (TAFC), has been successfully detected by mass spectrometry in serum, BALF and urine of patients with invasive aspergillosis, with promising sensitivities and specificities in single-centre studies. Intracellular uptake of siderophores has also been utilized for imaging, wherein fungal siderophores have been conjugated with the easy-to-produce radioactive isotope gallium-68 ( 68 Ga) to visualize infected body sites in PET. For the Scedosporium apiospermum complex, another siderophore N(α)-methyl coprogen B has been shown promising as a marker for airway colonization in early studies. SUMMARY: Siderophores and particular TAFC have the potential to revolutionize diagnostic pathways for invasive aspergillosis and other mould infections. However, larger multicentre studies are needed to confirm these promising performances. Methods that allow rapid and cost-effective measurements in routine clinical practice need to be developed, particularly when TAFC is used as a biomarker in patient specimens.

Pathogen Detection by Metagenomic Next-Generation Sequencing During Neutropenic Fever in Patients With Hematological Malignancies.

Background: Febrile neutropenia (FN) after chemotherapy is a major cause of morbidity during cancer treatment. The performance of metagenomic next-generation sequencing (mNGS) of circulating cell-free deoxyribonucleic acid from plasma may be superior to blood culture (BC) diagnostics for identification of causative pathogens. The aim of this study was to validate mNGS (DISQVER test) for the detection of pathogens in hematologic patients with FN. Methods: We collected paired whole blood specimens from central venous catheter and peripheral vein during FN for BC and mNGS testing. We repeated paired sampling at the earliest after 3 days of fever, which was defined as 1 FN episode. All clinical data were retrospectively reviewed by an infectious disease expert panel. We calculated percent positive agreement (PPA), percent negative agreement (PNA), percent overall agreement (POA), and sensitivity and specificity. Results: We analyzed a total of 98 unselected FN episodes in 61 patients who developed predominantly FN after conditioning therapy for allogeneic (n = 22) or autologous (n = 21) hematopoietic stem cell transplantation. Success rate of mNGS was 99% (97 of 98). Positivity rate of mNGS was 43% (42 of 97) overall and 32% (31 of 97) excluding viruses compared to 14% (14 of 98) in BC. The PPA, PNA, and POA between mNGS and BC were 84.6% (95% confidence interval [CI], 54.6% to 98.1%), 63.1% (95% CI, 51.9% to 73.4%), and 66% (95% CI, 55.7% to 75.3%), respectively. Sensitivity for bacteria or fungi was 40% (95% CI, 28.0% to 52.9%) and 18.5% (95% CI, 9.9% to 30.0%), respectively. Conclusions: Pathogen detection by mNGS (DISQVER) during unselected FN episodes shows 2-fold higher sensitivity and a broader pathogen spectrum than BC.

Isavuconazole plasma concentrations in critically ill patients during extracorporeal membrane oxygenation.

BACKGROUND: Isavuconazole is an antifungal drug used for treatment of invasive fungal infections. Critically ill COVID-19 and influenza patients require extracorporeal membrane oxygenation (ECMO) in cases with severe acute respiratory distress syndrome and have risk factors for invasive pulmonary aspergillosis. Little is known about isavuconazole plasma concentrations during ECMO. OBJECTIVES: To determine isavuconazole plasma concentrations in seven patients treated with intravenous isavuconazole under ECMO and the influence of the ECMO circuit immediately after the first isavuconazole dose. METHODS: Critically ill patients treated with isavuconazole (standard doses) and ECMO were included in this study. Sixty-four blood samples used for measurement of isavuconazole concentrations were collected at several timepoints starting 2 h after the first isavuconazole dose up to 168 h. An additional 27 blood samples were drawn from the inflow and outflow line of the membrane oxygenator to assess any potential isavuconazole clearance effect of the ECMO oxygenation device and the lines. RESULTS: Median isavuconazole trough levels above 1 µg/mL (min. 0.83, max. 1.73) or 2 µg/mL (min. 0.84, max. 2.97) were achieved 24 h or 96 h after the first dose of isavuconazole. The isavuconazole plasma concentrations pre (inflow line) and post (outflow line) the membrane oxygenator were directly correlated (ρ = 0.987, R2 = 0.994, P < 0.001). Post membrane oxygenator isavuconazole concentrations were directly correlated to contemporaneous samples obtained from the arterial lines of patients (ρ = 0.942, R2 = 0.945, P < 0.001). CONCLUSIONS: Isavuconazole concentrations might be influenced by the higher volume of distribution due to ECMO therapy, but were not altered by the ECMO oxygenator and achieved median plasma concentrations >1 µg/mL 24 h after the first loading dose.

Antifungal stewardship in solid organ transplantation.

BACKGROUND: Antifungal stewardship (AFS) has emerged as an important component of quality in managing invasive fungal infections (IFIs), and cost-benefit calculations suggest regular training in AFS is well worth the effort. METHODS: This review will discuss the most common IFIs in solid organ transplantation (SOT)-recipients, how to diagnose them, and current recommendations for antifungal treatment and prophylaxis before demonstrating key takeaway points of AFS in this high-risk population. RESULTS: Effective AFS starts before a patient is admitted for SOT, through education and regular interactions of the interdisciplinary clinical team involved in patient management, considering local factors such as epidemiological data and knowledge of diagnostic options including local turnaround times. Understanding the spectrum of antifungal agents, their efficacy and safety profiles, and pharmacokinetics, as well as duration of therapy is hereby essential. The most frequent IFIs in SOT recipients are caused by Candida species, followed by Aspergillus species, both with increasing resistance rates. Diagnosis of IFI can be challenging due to unspecific clinical presentation and difficult interpretation of microbiological findings and biomarkers. Prophylactic strategies, such as those for invasive aspergillosis in lung transplantation or invasive candidiasis (IC) in certain liver transplant settings, as well as the selection of the appropriate therapeutic agents require detailed knowledge on the pharmacokinetics and drug-drug interactions of antifungals. CONCLUSIONS: Here in this review, we address what constitutes good AFS in this heterogeneous field of solid organ transplant recipients.

Performance of the Euroimmun Aspergillus Antigen ELISA for the Diagnosis of Invasive Pulmonary Aspergillosis in Bronchoalveolar Lavage Fluid.

Invasive pulmonary aspergillosis (IPA) is a life-threatening disease that affects mainly immunocompromised hosts. Galactomannan testing from serum and bronchoalveolar lavage fluid (BALF) represents a cornerstone in diagnosing the disease. Here, we evaluated the diagnostic performance of the novel Aspergillus-specific galactomannoprotein (GP) enzyme-linked immunosorbent assay (ELISA; Euroimmun Medizinische Labordiagnostika) compared with the established Platelia Aspergillus GM ELISA (GM; Bio-Rad Laboratories) for the detection of Aspergillus antigen in BALF. Using the GP ELISA, we retrospectively tested 115 BALF samples from 115 patients with clinical suspicion of IPA and GM analysis ordered in clinical routine. Spearman's correlation statistics and receiver operating characteristics (ROC) curve analysis were performed. Optimal cutoff values were determined using Youden's index. Of 115 patients, 1 patient fulfilled criteria for proven IPA, 42 for probable IPA, 15 for putative IPA, 10 for possible IPA, and 47 did not meet criteria for IPA. Sensitivities and specificities for differentiating proven/probable/putative versus no IPA (possible excluded) were 74% and 96% for BALF GP and 90% and 96% for BALF GM at the manufacturer-recommended cutoffs. Using the calculated optimal cutoff value of 12 pg/mL, sensitivity and specificity of the BALF GP were 90% and 96%, respectively. ROC curve analysis showed an area under the curve (AUC) of 0.959 (95% confidence interval [CI] of 0.923 to 0.995) for the GP ELISA and an AUC of 0.960 (95% CI of 0.921 to 0.999) for the GM ELISA for differentiating proven/probable/putative IPA versus no IPA. Spearman's correlation analysis showed a strong correlation between the ELISAs (rho = 0.809, P < 0.0001). The GP ELISA demonstrated strong correlation and test performance similar to that of the GM ELISA and could serve as an alternative test for BALF from patients at risk for IPA.

Longitudinal Comparison of Automated SARS-CoV-2 Serology Assays in Assessing Virus Neutralization Capacity in COVID-19 Convalescent Sera.

CONTEXT.­: Serologic tests on automated immunology analyzers are increasingly used to monitor acquired immunity against SARS-CoV-2. The heterogeneity of assays raises concerns about their diagnostic performance and comparability. OBJECTIVE.­: To test sera from formerly infected individuals for SARS-CoV-2 antibodies by using 6 automated serology assays and a pseudoneutralization test (PNT). DESIGN.­: Six SARS-CoV-2 serology assays were used to assess 954 samples collected during a 12-month period from 315 COVID-19 convalescents. The tests determined either antibodies against the viral nucleocapsid (anti-NC) or spike protein (anti-S). Two assays did not distinguish between antibody classes, whereas the others selectively measured immunoglobulin G (IgG) antibodies. PNT was used to detect the presence of neutralizing antibodies. RESULTS.­: Comparison of qualitative results showed only slight to moderate concordance between the assays (Cohen κ < 0.57). Significant correlations (P < .001) were observed between the antibody titers from all quantitative assays. However, titer changes were not detected equally. A total anti-S assay measured an increase in 128 of 172 cases (74%) of a suitable subset, whereas all IgG anti-S tests reported decreases in at least 118 (69%). Regarding the PNT results, diagnostic sensitivities of 89% or greater were achieved with positive predictive values of at least 93%. In contrast, specificity changed substantially over time, varying from 20% to 100%. CONCLUSIONS.­: Comparability of serologic SARS-CoV-2 antibody tests is rather poor. Owing to different diagnostic specificities, the tested assays were not equally capable of capturing changes in antibody titers. However, with thoroughly validated cutoffs, IgG-selective anti-S assays are a reliable surrogate test for SARS-CoV-2 neutralizing antibodies in former COVID-19 patients.