Cobas Assay Research Articles

Confusion in the interpretation of prolactin levels caused by inappropriately low reference intervals.

Serum prolactin measurements are important in the differential diagnosis of pituitary masses and subfertility. We observed discrepancies in serum prolactin levels in several patients measured with different immunoassays. Despite differences in assay results, the reference intervals derived by the manufacturers were similar. In this study we aimed to investigate prolactin assay differences and to re-establish RIs for different prolactin immunoassays. For the assay comparison, serum samples were collected from men and women visiting our the Amsterdam UMC hospital. Prolactin levels were measured using the AtellicaTM IM analyzer (Siemens Healthineers) and the Cobas (Roche Diagnostics) immunoassay. Reference intervals for prolactin were re-established for men, premenopausal women and postmenopausal women for both the Atellica and Cobas immunoassay. Prolactin levels measured using the Cobas immunoassay were 1.75 times higher than those measured using the Atellica immunoassay. The re-established reference intervals for Atellica and Cobas confirmed these findings and were <0.32 U/L; <0.55 U/L for men; <0.64 U/L; <0.86 U/L for premenopausal women and <0.31 U/L; <0.59 U/L for postmenopausal women, respectively for Atellica and Cobas assays. The re-established RIs of the Atellica assay matched the current and manufacturer RIs whereas those for Cobas differed substantially. Prolactin levels are assay dependent and the re-established reference intervals are different for the Atellica and Cobas assays. We recommend that laboratory specialists and manufacturers periodically review prolactin assay RIs as incorrect reference intervals can lead to misinterpretation of prolactin levels and unnecessary referrals and further laboratory testing, as we have experienced.

Evaluation of assays for nucleic acid testing for the prevention of chikungunya and dengue virus transmission by blood transfusion.

The large dengue (DENV) and chikungunya (CHIKV) outbreaks observed during the last decade across the world, as well as local transmissions in non-endemic areas are a growing concern for blood safety. The aim of this study was to evaluate and compare the sensitivity of nucleic acid tests (NAT) detecting DENV and CHIKV RNA. Using DENV 1 to 4 International Standards, the limits of detection (LODs) calculated by probit analysis of two NAT assays; the cobas CHIKV/DENV assay (Roche Diagnostics) and the Procleix Dengue Virus Assay (Grifols) were compared. In addition, CHIKV-RNA LOD of the cobas CHIKV/DENV assay was evaluated. For dengue, the 95% LOD of the cobas assay ranged between 4.10 [CI95%: 2.70-8.19] IU/mL (DENV-2) and 7.07 [CI95%: 4.34-14.89] IU/mL (DENV-4), and between 2.19 [CI95%: 1.53-3.83] IU/mL (DENV-3) and 5.84 [CI95%: 3.84-10.77] IU/mL (DENV-1) for Procleix assay. The Procleix assay had a significant lower LOD for DENV-3 (2.19 vs. 5.89 IU/mL) when compared to the cobas assay (p = 0.005). The 95% LOD for CHIKV-RNA detection of the cobas assay was 4.76 [CI95%: 3.08-8.94] IU/mL. The two NAT assays developed for blood donor screening evaluated in this study demonstrated high and similar analytical performance. Subject to an appropriate risk-benefit assessment, they can be used to support blood safety during outbreaks in endemic areas or in non-endemic areas as an alternative to deferring blood donors during local transmission likely to affect the blood supply. The development of multiplex assays is expected to optimize laboratory organization.

US-based, Prospective, Blinded Study of Thyrotropin Receptor Antibody in Autoimmune Thyroid Disease.

Bioassays provide information on the functionality of thyrotropin receptor antibodies (TSH-R-Ab) and thus may offer more clinical utility than binding assays. In this prospective, blinded, US-based study, the clinical performance of several TSH-R-Ab assays was compared. US endocrinology clinic. One hundred sixty-two unselected, consecutive, well-documented patients with various thyroid diseases and healthy controls. Blinded TSH-R-Ab measurements. Sensitivity and specificity of 4 TSH-R-Ab assays. The 4 TSH-R-Ab assays were negative in all 42 patients without autoimmune thyroid disease (AITD). In 104 patients with Graves' disease (GD), irrespective of the disease duration, TSH-R-Ab positivity was present in 65 (63%), 67 (65%), and 87 (84%) for the Cobas and Immulite binding assays and stimulatory TSH-R-Ab [thyroid-stimulating immunoglobin (TSI)] bioassay, respectively (TSI vs Immulite P < .0025, TSI vs Cobas P < .0009). Fifteen newly diagnosed GD patients were all positive in the TSI bioassay, but only 11 (73%) were positive in the Cobas and Immulite binding assays. Nine GD patients with biochemical subclinical hyperthyroidism were TSI-positive but Immulite- and Cobas-negative. Two GD patients were blocking TSH-R-Ab [thyroid-blocking immunoglobin (TBI)]-positive and TSI-negative, and the Immulite and Cobas were positive in both. Additional serum samples from AITD patients that consisted of 30 TBI-positive and 10 TSI-positive samples were blindly tested in the binding assays. Only 6 of the 10 TSI-positive samples were positive in both binding assays, and 30 and 28 of the TBI-positive samples were positive in the Cobas and Immulite assays, respectively. Binding TSH-R-Ab assays are less sensitive than TSI bioassays and are not specific for stimulating antibodies. Measuring the function of TSH-R-Ab in a bioassay can provide useful information to clinicians.

Analysis of Serum Free Thyroxine Concentrations in Healthy Term Neonates Underlines Need for Local and Laboratory-Specific Reference Interval: A Systematic Review and Meta-Analysis of Individual Participant Data.

Background: Initial evaluation of the hypothalamus-pituitary-thyroid axis is done by measuring serum free thyroxine (fT4) and thyrotropin concentrations. For correct interpretation of these measurements, reliable age-specific reference intervals (RIs) are fundamental. Since neonatal fT4 RIs conforming to the Clinical and Laboratory Standards Institute guidelines are not available for all assays, we set out to create literature-based uniform age-specific neonatal fT4 RIs that may be used for every assay. Methods: For meta-analysis of individual participant fT4 concentrations, we systematically searched MEDLINE and Embase (search date December 6, 2023; PROSPERO registration CRD42016041871). We searched for studies reporting fT4 concentrations in healthy term newborns aged 2-27 days, born to mothers without thyroid disease in iodine-sufficient regions. Authors were invited to supply data. Due to standardization differences between assays, data could not be combined for meta-analysis directly, and we attempted to normalize the data using two distinct methods. Results: We obtained 4206 fT4 concentrations from 20 studies that used 13 different assays from 6 manufacturers. First, we set out to normalize fT4 data using the mean and standard deviation of (assay-specific) adult RIs. fT4 concentrations were transformed into Z-scores, assuming a normal distribution. Using a linear mixed-effects model (LMM), we still found a significant difference between fT4 concentration across studies (p < 0.001), after this normalization. As a second approach, we normalized the fT4 concentrations using data from a method/assay comparison study. We used the relationship between the Cobas assay and the other assays as a reference point to convert all values to Cobas values. However, this method also failed to produce consistent results, with significant differences between the normalized data (LMM p < 0.001). Conclusions: We conclude that our attempts at normalizing fT4 assay results were unsuccessful. Confounders related to our unsuccessful analysis may be assay related and/or biological. These findings have significant implications for patient care, since relying on RIs from literature may result in erroneous interpretation of results. Therefore, we strongly recommend to establish local RIs for accurate interpretation of serum fT4 concentrations in neonates.

Clinical Evaluation of the Alinity m STI Multiplex PCR Assay.

Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are routinely tested and reported; however, Trichomonas vaginalis (TV) is the most common sexually transmitted infection (STI) in the United States and the prevalence of Mycoplasma genitalium (MG) infections is likely higher than estimated. We examined the clinical performance of the Alinity m STI assay for detection and surveillance of CT/NG/TV/MG in urine specimens from patients at a large academic medical center. Urine specimen from 198 patients was tested in this evaluation. Alinity m STI and Aptima Combo 2 CT/NG and TV assay (Panther System) results were compared, with discrepant results run on the cobas 6800 CT/NG, TV/MG assays. Analyzer turnaround times, time from loading the specimen on the analyzer to results reporting, were determined for Alinity m and Panther systems. Overall percent agreements of the Alinity m in comparison with the Aptima and cobas assays for CT, NG, TV, and MG were 99.5% (97.2%, 99.9%), 99.5% (97.2%, 99.9%), 98.4% (95.5%, 99.5%), and 86.4% (66.7%, 95.3), respectively. There were 5 discrepant samples (CT, 1; NG, 1; TV, 3) between the Alinity m and the Aptima assays, and 3 MG discrepant samples between the Alinity m STI and cobas 6800. Two of the 5 Aptima and Alinity m discrepant samples were resolved as they yielded similar results on both Alinity m and cobas 6800. TV and MG infections comprised 54% of the positive samples and were more often asymptomatic than CT and NG infections. Analyzer turnaround time was 3 hours 25 minutes for the Aptima CT/NG, 3 hours 25 minutes for Aptima TV, and 1 hour 55 minutes for Alinity m STI assay. The Alinity m STI assay allows for fast and simultaneous detection of the 4 major STI pathogens, which can facilitate surveillance and provide accurate results to help clinicians diagnose for initiation of appropriate treatment.

Detection of EGFR T790M mutation using liquid biopsy for non-small cell lung cancer: Utility of droplet digital polymerase chain reaction vs. cobas real-time polymerase chain reaction

BackgroundDigital platforms for mutation detection yield higher sensitivity than non-digital platforms but lack universal positive cut-off values that correlate with the outcome of osimertinib treatment. This study determined compared droplet digital polymerase chain reaction (ddPCR) to the standard cobas assay for epithelial growth factor receptor (EGFR) T790M mutation detection in patients with non-small cell lung cancer. MethodsStudy patients had EGFR-mutant tumours with disease progression on first/second generation EGFR tyrosine kinase inhibitors, and osimertinib treatment after T790M mutation detection. T790M status was tested by cobas assay using liquid biopsy, and only by ddPCR if an EGFR mutation was identified but T790M was negative. Clinical efficacy of osimertinib was compared between patients with T790M detected by cobas vs. only by ddPCR. A positive cut-off value for ddPCR was determined by assessing efficacy with osimertinib. Results61 patients had tumors with an acquired T790M mutation, 38 detected by cobas and an additional 23 only by ddPCR. The median progression-free survival (PFS) for the cobas- and ddPCR-positive groups was 9.5 and 7.8 months, respectively (p=0.43). For ddPCR, a fractional abundance (FA) of 0.1% was used as a cut-off value. The median PFS of patients with FA ≥0.1% and <0.1% was 8.3 and 4.6 months, respectively (p=0.08). FA ≥0.1% was independently associated with a longer PFS. ConclusionUsing ddPCR to follow up the cobas assay yielded more cases (38% of total) with a T790M mutation. A cut-off value of FA ≥0.1% identified patients who responded as well to osimertinib as those identified by cobas assay. This sequential approach should detect additional patients who might benefit from osimertinib treatment.

Clinical Validation of the Unparalleled Sensitivity of the Novel Allele-Discriminating Priming System Technology-Based EGFR Mutation Assay in Patients with Operable Non-Small Cell Lung Cancer.

Recently, we developed allele-discriminating priming system (ADPS) technology. This method increases the sensitivity of conventional quantitative polymerase chain reaction up to 100 folds, with limit of detection, 0.01%, with reinforced specificity. This prospective study aimed to develop and validate the accuracy of ADPS epidermal growth factor receptor (EGFR) Mutation Test Kit using clinical specimens. In total 189 formalin-fixed paraffin-embedded tumor tissues resected from patients with non-small cell lung cancer were used to perform a comparative evaluation of the ADPS EGFR Mutation Test Kit versus the cobas EGFR Mutation Test v2, which is the current gold standard. When the two methods had inconsistent results, next-generation sequencing-based CancerSCAN was utilized as a referee. The overall agreement of the two methods was 97.4% (93.9%-99.1%); the positive percent agreement, 95.0% (88.7%-98.4%); and the negative percent agreement, 100.0% (95.9%-100.0%). EGFR mutations were detected at a frequency of 50.3% using the ADPS EGFR Mutation Test Kit and 52.9% using the cobas EGFR Mutation Test v2. There were 10 discrepant mutation calls between the two methods. CancerSCAN reproduced eight ADPS results. In two cases, mutant allele fraction was ultra-low at 0.02% and 0.06%, which are significantly below the limit of detection of the cobas assay and CancerSCAN. Based on the EGFR genotyping by ADPS, the treatment options could be switched in five patients. The highly sensitive and specific ADPS EGFR Mutation Test Kit would be useful in detecting the patients who have lung cancer with EGFR mutation, and can benefit from the EGFR targeted therapy.

Growth Differentiation Factor-15 in Patients Recovering From Acute Coronary Syndromes

Plasma concentrations of growth differentiation factor-15 (GDF-15) are known to be prognostic in patients with acute coronary syndromes (ACS). However, the pattern of GDF-15 in the months post-ACS remains uncertain. This study aimed to investigate the temporal pattern of circulating GDF-15 in the intermediate to long-term post-ACS. The Biomarker-guided Risk Management following Acute Coronary Syndrome (BioMACS) clinical trial enrolled patients between 1 month and 12 months post-discharge after an ACS. Patients were selected from the trial Usual Care arm, with equal numbers of non-ST elevation myocardial infarction (NSTEMI) and STEMI. Groups were matched by time from ACS. GDF-15 was measured at baseline and 3 months using the ROCHE Cobas assay. Sixty patients were included, 30% were female, and the median age was 67 years. Ethnicity was 81% European, 2% Māori, 7% Pacific, 7% Asian, and 3% Indian. For the whole group, mean GDF-15 concentrations were 1,430 (standard deviation [SD] 632) pg/mL at baseline, and 1,348 (SD 626) pg/mL at 3 months. No significant differences in GDF-15 concentrations were found between NSTEMI and STEMI groups at both timepoints. The change from baseline to 3 months was –93 (SD 462) pg/mL, with no statistically significant difference in the change between the NSTEMI and STEMI groups. GDF-15 was related to age, systolic blood pressure, and measures of renal function (creatinine and estimated glomerular filtration rate). GDF-15 concentrations were elevated in the months post-ACS but remained stable over a further 3-month period. The prognostic role of this biomarker in the convalescent period post-ACS needs to be assessed in future research studies.

Clinical performance evaluation of the Aptima viral assays for the quantitation of HIV-1, HCV, and HBV in plasma samples

The clinical performance of the Aptima® HIV-1 Quant Dx, Aptima HCV Quant Dx, and Aptima HBV Quant Dx were evaluated and compared to the Roche cobas HIV-1, HCV, and HBV assays performed on the Roche cobas 6800 system. The Aptima Quant assays exhibited an overall percent agreement of 99.4% for HBV, 98.3% for HCV, and 85.14% for HIV-1. The average log difference between the Aptima and Roche assays was below 0.2 IU (or copies)/mL and the quantitative correlation's (R-squared value (R2)) was between 0.95 and 0.97. The Aptima viral assays demonstrated a high level of quantitative correlation with the Roche cobas assays for HCV, HBV, and HIV-1.

Comparison between liquid chromatography-tandem mass spectrometry and immunoassay methods for measurement of plasma 25 (OH) vitamin D

Abstract Objectives Vitamin D is one of the major hormones involved in the metabolism of calcium (Ca) and phosphorus (P). In the present study, we aimed to determine the analytical performance of the immunoassay method used for determining plasma 25-hydroxyvitamin D [25(OH)D] levels in routine clinical practice in laboratories. Methods Venous blood samples were collected from 156 patients for the comparisons and were analyzed with Siemens ADVIA Centaur XPT, the Roche Cobas 6,000’s module e601, Abbott Architect i2000, and the liquid chromatography with tandem mass spectrometry (LC-MS/MS). Results The four methods were analyzed and compared through the Passing-Bablok regression for 25(OH)D, and the highest correlation was found at LC-MS/MS and Cobas 6,000’s module e601 (r=0.799), LC-MS/MS/Abbott Architect i2000, and LC-MS/MS/Siemens ADVIA Centaur XPT as r=0.736, 0.721, respectively. The correlation coefficient was found between Abbott Architect i2000 with Roche Cobas e601 and Siemens ADVIA Centaur XPT as r=0.934 and r=0.907, respectively. Also, the correlation coefficient was found between Roche Cobas e601 and Siemens ADVIA Centaur XPT as r=0.906. Conclusions The Roche Cobas assay showed better performance, compared with the other assays. Based on our findings, the chemiluminescence methods in automated systems seem to be expedient.

Concordance between the BD Onclarity and Roche cobas assays for detection of HPV DNA in a Chinese population.

As cervical cancer screening shifts from cytology to human papillomavirus (HPV) testing, a major issue involves validating more HPV tests. In recent years, some HPV tests are used for clinical performance verification in China. The purpose of this study was to explore whether the BD Onclarity (Becton, Dickinson and Company)HPV assay differs from the Roche cobas(Roche Molecular Systems)HPV assay, as determined using 944 cervical samples, including 588 with sequencing results. In the nucleic acid assay accuracy verification, the assays showed excellent concordance for detection of HPV16 (κ = 0.93, 95% confidence interval [CI]: 0.89-0.97) and HPV18 (κ = 0.90, 95% CI: 0.83-0.97), and very good concordance for the 12 other high-risk types (HPV31/33/35/39/45/51/52/56/58/59/66/68, κ = 0.79, 95% CI: 0.75-0.83). The overall agreement for HPV DNA detection between Onclarity and cobas was very good (κ = 0.7755). No difference for ≥CIN2 sensitivity was observed between Onclarity and cobas (both 96.5%), whereas the ≥CIN2 specificity for detection of Onclarity (16.6%, 95% CI: 13.7-19.9) was higher than that of cobas (11.5%, 95% CI: 9.1-14.5). Onclarity exhibited comparable screening performance and triage efficiency compared to cobas in the detection of cervical disease in Chinese women.

Assessment of the cobas® HBV RNA investigational assay in the setting of nucleoside analog therapy cessation.

HBV RNA is used as a marker of cccDNA transcription and is applicable in the setting of nucleos(t)ide analog (NA) treatment, which suppresses HBV DNA. Traditional assays for quantification of HBV RNA rely on labor-intensive 3'RACE assays targeting the polyA tail. In this study, the high-throughput Roche cobas®HBV RNA investigational assay was assessed on the Roche cobas® 6800 automated platform. Of 969 samples collected for a NA treatment cessation trial, and tested on the cobas assay, 249 were analyzed for sensitivity, reproducibility, sample type applicability, and results were compared to a RACE-based assay. Results of 97 paired serum and plasma samples demonstrated an excellent correlation of 0.98. However, 14.5% of plasma samples yielded detectable (below the limit of quantification) results, when the paired serum was undetectable, and plasma was shown to yield a statistically significant (p < 0.001) greater mean 0.119 log10 copies/ml. Quantification of 152 samples showed good correlation (0.91) between the cobas and RACE assays. The cobas assay demonstrated superior lower limit of quantification, 10 copies/ml, which resulted in detection of 13.2% more samples than the RACE assay. Reproducibility and linear range of the automated assay were also confirmed. The Roche cobas assay for HBV RNA is sensitive and highly recommended.

Prevalence of high-risk human papilloma virus infection and cervical cytological abnormalities in female Turkish patients with rheumatologic disease

Background/Aim: It is believed that patients with rheumatological diseases (RDs) are more prone to infectious diseases, possibly due to both disease-related immune dysfunction and chronic inflammation, and immunosuppressive agents used in the treatment of rheumatological diseases. In this context, we aimed to evaluate the prevalence of high-risk human papillomavirus (Hr-HPV) infection and cervical cytological abnormalities in Turkish female patients with RDs and compare them with healthy controls (HCs). Methods: 362 sexually active patients with RDs followed up between January 2014 and June 2021 were included in this cross-sectional study. Patients with RDs were classified as autoimmune and non-autoimmune groups according to seropositivity. Data of 883 age-matched HCs were used for comparison. Demographic features, cervical cytology reports of the patients and HPV test results were retrieved from hospital database. Cervical cytological abnormalities was categorized according to Bethesda 2014. Cobas assay was used for detecting and typing for Hr-HPV. Results: The RDs group and the HCs group were similar in terms of mean age, BMI, and rate of smokers (P>0.05). Cytological evaluation was carried out in all of 362 patients with RDs (161 autoimmune and 201 non-autoimmune) and in all of 883 HCs. HPV test was applied in 286 patients with RDs and 776 of HCs. 16 (4.4%) patients with RDs and 58 (6.6%) HCs had cervical cytological abnormality. Of the patients who underwent HPV testing; 22 (7.7%) patients with RDs and 75 (9.7%) HCs had Hr-HPV. The prevalence of cervical cytologic abnormalities and Hr-HPV infection rate were similar between patient groups and HCs (P=0.186 and P=0.400, respectively). Conclusion: It was determined that chronic systemic inflammation, which plays a role in the pathogenesis of rheumatological diseases, and immunosuppressive agents used in the treatment did not increase the prevalence of Hr-HPV infection and cervical cytological abnormalities.

A community-based approach to cervical cancer prevention in western Kenya: An AMPATH feasibility project.

Objectives:Centralized programs have been ineffective in reducing the burden of cervical cancer among Kenyan women. A community-based pilot study was initiated to screen Kenyan women for cervical cancer and to vaccinate their children against human papillomavirus (HPV).Methods:Women were educated about cervical cancer prevention at community meetings. Women then provided self-collected vaginal swabs for oncogenic HPV testing using the Roche Cobas Assay. All women were then referred to the local clinic for Visual Inspection with Acetic Acid (VIA). Women were offered the quadrivalent HPV vaccine for their children if and when it became available for the study.Results:Women in western Kenya were invited to participate in community meetings. A total of 200 women were enrolled: 151 (75.5%) were HIV-uninfected and 49 (24.5%) were HIV-infected; the median age for all women was 42 years. High-risk (HR)-HPV types were detected in 49 of swabs from all 200 participants (24.5%) including 20.5% of HIV-uninfected women and 36.7% of HIV-infected women (P = .022). VIA was performed on 198 women: 192 had normal examinations and six had abnormal examinations. Five cervical biopsies revealed two cases of CIN 2 and one CIN 3. Although all mothers were willing to have their children (N = 432) vaccinated, the HPV vaccine could not be delivered to Kenya during the study period.Conclusions:Kenyan women were willing to attend community meetings to learn about prevention of cervical cancer, to provide self-collected vaginal swabs for HPV testing, to travel to the Webuye Clinic for VIA following the collection of swabs, and to have their children vaccinated against HPV. HR-HPV was prevalent, especially in HIV-infected women. As a result of this pilot study, this community-based strategy to prevent cervical cancer will be continued in western Kenya.

Detection of Neisseria gonorrhoeae or Chlamydia trachomatis from oral wash specimens using the Abbott RealTime CT/NG assay and the Cobas 4800 CT/NG assay: A prospective study

IntroductionIsolating oropharyngeal Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) from oral wash specimens (OWSs) is uncommon. Therefore, we evaluated the performance of the Abbott RealTime CT/NG assay and the Cobas 4800 CT/NG assay in detecting NG and CT in OWSs. MethodsThis multicenter prospective study included 457 patients from 14 medical facilities suspected of having untreated male urethritis or female cervicitis from November 2014 to December 2015. OWSs were collected and tested using the Abbott and Cobas assays. Finally, the discordant results were confirmed using the APTIMA Combo 2 transcription-mediated amplification assay and retested using each assay. ResultsThe sensitivity and specificity of the Abbott assay were 100% and 97.2% for NG and 87.5% and 100% for CT, respectively, and of the Cobas assay were 100% and 98.8% for NG and 93.8% and 99.8% for CT, respectively. Both assays had high negative but low positive predictive values for oropharyngeal NG (Abbott assay: 65.7%, Cobas assay: 82.1%). Based on the definition of “true positive,” the prevalence of oropharyngeal NG and CT were 5.0% and 3.5%, respectively. ConclusionsThe Abbott and Cobas assays using OWSs had high sensitivity and specificity, which can help diagnose oropharyngeal NG and CT. We consider that if a positive result is obtained, the patient should be treated because the negative predictive values were high. However, limited data are available on oropharyngeal NG and CT detection, and further studies are needed to clarify the role of oropharyngeal sexually transmitted infections.

147. Defining the Optimal Serial Testing Interval and Features for Identifying Patients with Early SARS-CoV-2 Infection

BackgroundSerial testing for SARS-CoV-2 is necessary to prevent spread from patients early in infection. Testing intervals are largely derived from viral kinetic studies performed early in the COVID-19 pandemic. Laboratory and epidemiologic data accrued over the past year present an opportunity to use empiric models to define optimal serial testing intervals and features predictive of early infection.MethodsRetrospective analysis of 15,314 inpatients within the Mass General Brigham healthcare system who had two tests within a 36-hour period between May 1 2020 and May 29 2021. Early infection was defined as having a negative test followed by a positive test. Patients with prior positive tests were excluded. The primary outcome was the proportion of patients in early infection over the total number tested serially, stratified by 4-hour testing intervals from the timestamp of the first test. Multivariate modeling was used to identify features predictive of early infection. Covariates included demographics, body site, PCR assay, location, community incidence, percent positivity, and median / skew of Ct value distributions. ResultsOf 19,971 test pairs, 193 (0.97%) were characterized as a negative followed by a positive within 36 hours. Bivariate analysis showed a close association between negative to positive test pairs during the first surge in spring 2020 that was not present during the winter surge. Negative to positive test pairs were most common in the 12 to 16 hour time interval (51/193, 26%, Figure 1). After controlling for covariates, the Roche cobas assay was more likely to identify patients with a negative to positive test pair relative to the Cepheid Xpert, Hologic Panther Fusion and Roche Liat assays. A second specimen from the lower respiratory tract was more likely to lead to a positive relative to other body sites. Community incidence and Ct value distributions were not predictive and there were no differences between nasal and nasopharyngeal swabs. All 4-hour time intervals from 16 to 36 hours were significant for predicting a negative to positive test pair (Table 1).Figure 1. Distribution of negative to positive test pairs by 4 hour time intervals Table 1. Multivariate regression predicting a negative to positive test pair ConclusionThe likelihood of detecting early infection is dependent on PCR platform and body site of sampling. A range of time intervals between 16 to 36 hours after the initial test were likely to identify positive cases.Disclosures Sanjat Kanjilal, MD, MPH, GlaskoSmithKline (Advisor or Review Panel member)

FC 056ESTIMATING ALBUMIN TO CREATININE RATIO FROM PROTEIN TO CREATININE RATIO USING SAME DAY MEASUREMENT: VALIDATION OF EQUATION

Abstract Background and Aims According to the KDIGO, severity of chronic kidney disease is defined by glomerular filtration rate and albuminuria. Furthermore, these variables are used for estimating both cardiovascular and end-stage renal disease risk. However, albuminuria is not always available, whereas proteinuria is, notably because of the lower costs of proteinuria. Recently, Weaver &amp; al. developed an equation that estimates urine albumin/creatinine ratio (ACR) from protein/creatinine ratio (PCR). For retrospective analyses in clinical research, it might be interesting to be able to estimate ACR from PCR. The objective of this paper is to assess the performance of Weaver &amp; al. ‘s equation in our population. Method In a University hospital, we retrospectively analysed measurement of ACR and PCR obtained on the same day between May 2018 and March 2020. Different assays were considered to measure urine albumin, creatinine and protein (Roche Cobas from May 2018 to May 2019 and Abbott Alinity from May 2019 to March 2020). Only one (the first available) sample per patient was considered. Patients were then categorized according to the KDIGO classification (A1-A2-A3). We then compared categorization of patients according to KDIGO between measured and estimated ACR. Sensitivity, specificity, positive predictive value and negative predictive value of estimated ACR versus measured ACR were calculated considering two different thresholds: A1 versus A2/3 (ACR 30mg/g) or A1/A2 versus A3 (ACR 300mg/g). Results Comparison was done in 2633 and 2386 patients, with Cobas and Alinity, respectively. Median age was 63 (IQR 19) and 64 (IQR 19) years old, 43 and 41% were women and 74 and 78% were diabetic (albuminuria measurement is refunded for diabetic patients in Belgium) with Cobas and Alinity, respectively. Considering measured ACR, patients were categorized in A1, A2, A3 in 65,6%, 25,5%, and 8,8%, respectively with the Cobas assay. With the Alinity assay, the results were 64,2%, 25,5%; and 10,3%, respectively. Considering estimated ACR, patients were categorized in A1, A2, A3 in 64,7%, 25,7%, and 9,6%, respectively with the Cobas Assay. With the Alinity assay, the results were 62,5%, 25,8% and 11,7%, respectively. Regarding A1-A2 (30mg/g) threshold, sensitivity was 85% and 89%, specificity was 91% and 92%, positive predictive value was 83% and 85%, negative predictive value was 92% and 94% for Cobas and Alinity respectively. Regarding A2-A3 (300mg/g) threshold, sensitivity was 93% and 98%, specificity was 98% for both, positive predictive value was 86% and 87%, negative predictive value was 99% and 99,8% for Cobas and Alinity respectively. Values are presented in table 1. Conclusion We observed a good concordance between estimated and measured ACR. Particularly, no patient in category A3 with measured ACR was categorized A1 with the estimating equations. We also observed that concordance was good regardless of our available assays. Thus, negative predictive value was excellent. In conclusion, ACR should be measured when clinically needed, but an estimated ACR can reasonably be obtained from Weaver’s equation and may provide an accurate estimation for retrospective clinical research.

Reliable detection of SARS-CoV-2 with patient-collected swabs and saline gargles: A three-headed comparison on multiple molecular platforms

With increasing demands for SARS-CoV-2 testing, as well as the shortages for testing supplies, collection devices, and trained healthcare workers (HCWs) to collect specimens, self-collection is an attractive prospect to reduce the need for HCWs and expenditure of personal protective equipment. Apart from the traditional nasopharyngeal swab used for SARS-CoV-2 detection, alternative specimens have been validated such as a combined swabs of the oropharynx and anterior nares (OP/N), or throat samples using saline gargles. Both the alternative specimen types are amenable to self-collection. Objectives. This study aimed to compare the sensitivity of HCW-collected (OP/N) swabs, self-collected OP/N swabs, and self-collected saline gargles. Among 38 individuals previously testing positive for SARS-CoV-2 (or their close contacts), two self-collected specimen types (OP/N and saline gargles) were compared to HCW-collected OP/N swabs. SARS-CoV-2 testing was performed on three molecular assays: a laboratory-developed test (LDT), and two commercial assays on automated platforms: Cobas 6800 (Roche Diagnostics) and Panther (Hologic). The sensitivity of self-collected OP/N swabs was equivalent to healthcare worker (HCW)-collected OP/N swabs at 100.0 % [92.6%–100.0%] for all three molecular tests. The sensitivity of saline gargles was not significantly different than HCW-collected OP/N swabs, but varied slightly between instruments at 93.8 % [85.9%–93.8%] for the LDT, 96.8 % [88.6%–96.8%] for the Cobas assay, and 96.7 % [89.2%–96.9%] for the Panther assay. Overall, self-collection using OP/N swabs or saline gargles are reasonable alternatives to HCW-based collections for SARS-CoV-2 detection, and could facilitate broader surveillance strategies.

Performance of an automated chemiluminescent immunoassay for SARS-COV-2 IgM and head-to-head comparison of Abbott and Roche COVID-19 antibody assays

IntroductionWe evaluated the performance of the new Abbott SARS-CoV-2 IgM assay on the Architect immunoassay analyser and compared it to the Architect IgG/Roche Cobas total antibody assays in both SARS-CoV-2 RT-PCR positive cases and healthy controls. Method200 healthy control samples and 48 individuals with other antibody-positive disorders (18 hepatitis/18 dengue/11 ANA/1 dsDNA) served to assess for potential cross-reactivity. Anonymised residual leftover sera positive for SARS-CoV-2 on RT-PCR were recruited as cases (N ​= ​133). The sensitivity/specificity/cross-reactivity of the Architect IgM assay were assessed. Concordance between the 3 assays were also analysed. ResultsThere was no cross-reactivity with controls and other antibody positive samples. The Architect IgM assay was 100% specific (95% CI 98.5 to 100) and sensitivity was 77.8% (95% CI 60.8 to 89.9) ≥14 days post-first positive RT-PCR (POS). Sensitivity of the combined Architect IgM and IgG results (30.8%) was significantly better than the Cobas total antibodies (15.4%) in early disease (p ​= ​0.04). While the Architect IgM assay had moderate agreement with the Cobas total antibody result (Cohen’s kappa 0.72), a combined Architect IgM and IgG result had better agreement (Cohen’s kappa 0.83). ConclusionThe Architect IgM assay has good specificity and no cross-reactivity with other antibody positive cases. A combined Architect IgM and IgG result has better sensitivity than the individual assays for early COVID-19. The Architect IgM assay is not comparable to the Cobas total antibody assay, but the Architect IgM and IgG combined result has good agreement with the Cobas assay.

Clinical performance of Roche cobas 6800, Luminex ARIES, MiRXES Fortitude Kit 2.1, Altona RealStar, and Applied Biosystems TaqPath for SARS‐CoV‐2 detection in nasopharyngeal swabs

We compared the performance of five assays for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) detection on nasopharyngeal swab samples: Roche “cobas,” Luminex “ARIES,” MiRXES “Fortitude,” Altona “RealStar,” and Thermo Fisher Scientific “TaqPath.” A total of 94 nasopharyngeal swab samples were obtained from 80 confirmed coronavirus disease 2019 cases in the first 2 weeks of illness (median, 7 days; range, 2–14 days) and 14 healthy controls. After collection, all samples were transported to the hospital clinical laboratory within 24 h. These samples were tested on all five assays within 3 days of sample receipt. Of the 94 samples, 69 yielded the same result on all platforms, resulting in an agreement of 73.4% (69 of 94). Of these, 14 were the healthy control swabs which all tested negative, demonstrating good specificity across all platforms. The ARIES assay had the lowest detection rate (68.8%), followed by Fortitude (85.0%), RealStar (86.3%), cobas (95.0%), and TaqPath (100%). Statistically significant differences were observed for ARIES, Fortitude, and RealStar when compared against the best performing TaqPath using McNemar's χ 2 test. A consensus result was established based on the results obtained by the cobas, Fortitude, RealStar, and TaqPath. Six discrepancies had failed to reach a consensus and were adjudicated using the Cepheid Xpert Xpress SARS‐CoV‐2. Overall, the TaqPath and cobas assays were the most sensitive at detecting their designated SARS‐CoV‐2 gene targets. On the other hand, the ARIES assay was the least sensitive, thus warranting the need for assay re‐optimization before go‐live at the testing laboratory.