371. Estimating SARS-CoV-2 Seroprevalence from Spent Blood Samples, January–March 2021

Background Measuring SARS-CoV-2 antibody prevalence in spent samples at serial time points can determine seropositivity in a diverse pool of individuals to inform understanding of trends as vaccinations are implemented. Methods Blood samples collected for clinical testing and then discarded ("spent samples") were obtained from the clinical laboratory of a medical center in Atlanta. A convenience sample of spent samples from both inpatients (medical/surgical floors, intensive care, obstetrics) and outpatients (clinics and ambulatory surgery) were collected one day per week from January-March 2021. Samples were matched to clinical data from the electronic medical record. In-house single dilution serological assays for SARS-CoV-2 receptor binding domain (RBD) and nucleocapsid (N) antibodies were developed and validated using pre-pandemic and PCR-confirmed COVID-19 patient serum and plasma samples (Figure 1). ELISA optical density (OD) cutoffs for seroconversion were chosen using receiver operating characteristic analysis with areas under the curve for all four assays greater than 0.95 after 14 days post symptom onset. IgG profiles were defined as natural infection (RBD and N positive) or vaccinated (RBD positive, N negative). Figure 1. Nucleocapsid serology assay validation Single dilution serological assays for SARS-CoV-2 nucleocapsid antibodies were validated using pre-pandemic and PCR-confirmed COVID-19 patient serum and plasma samples. ELISA optical density (OD) cutoffs for seroconversion were chosen using receiver operating characteristic (ROC) analysis with areas under the curve (AUC) for all four assays greater than 0.95 after 14 days post symptom onset. Results A total of 2406 samples were collected from 2132 unique patients. Median age was 58 years (IQR 40-70), with 766 (36%) ≥ 65 years. The majority were female (1173, 55%), and 1341 (63%) were Black. Median Elixhauser comorbidity index was 5 (IQR 2-9). 210 (9.9%) patients ever had SARS-CoV-2 detected by PCR, and 191 (9.0%) received a COVID-19 vaccine within the health system. Nearly half (1186/2406, 49.3%) of samples were collected from inpatient units, 586 (24.4%) from outpatient labs, 403 (16.8%) from the emergency department, and 231 (9.6%) from infusion centers. Overall, 17.0% had the IgG natural infection profile, while 16.2% had a vaccination profile. Prevalence estimates for IgG due to natural infection ranged from 24.0% in week 2 to 9.7% in week 5, and for IgG due to vaccine from 4.4% in week 2 to 32.0% in week 6 (Table, Figure 2). Table. SARS-CoV-2 antibody seropositivity by week of sample collection for spent routine blood chemistry samples. RBD = receptor binding domain. N = nucleocapsid. Seropositivity defined by enzyme-linked immunoassay (ELISA) optical density cutoffs selected using receiver operating characteristic analysis with areas under the curve (AUC) for all four assays greater than 0.95 after 14 days post symptom onset. IgG defined as positive if both RBD and N seropositive. Figure 2. RBD and Nucleocapsid seropositivity to differentiate natural infection vs. vaccination by week of sample collection. RBD = receptor binding domain. N = nucleocapsid. Seropositivity defined by enzyme-linked immunoassay (ELISA) optical density cutoffs selected using receiver operating characteristic analysis with areas under the curve (AUC) for all four assays greater than 0.95 after 14 days post symptom onset. Conclusion Estimated SARS-CoV-2 IgG seroprevalence among patients at a medical center from January-March 2021 was 17% by natural infection, and 16% by vaccination. Weekly trends likely reflect community spread and vaccine uptake. Disclosures Daniel Graciaa, MD, MPH, MSc, Critica, Inc (Consultant)

CXCL9 as a key biomarker of vitiligo activity and prediction of the success of cultured melanocyte transplantation

This study aimed to investigate the potential biomarkers of vitiligo by evaluating the disease activity and curative effect of autologous cultured pure melanocyte transplantation (CMT) on patients. Altogether, 36patients with stable vitiligo were treated with CMT. Blister fluid samples were collected from patients with stable vitiligo. Patients with active vitiligo were matched with healthy controls. The chemokine levels in the serum and blister fluid samples were measured using Luminex. The curative effect on patients with stable vitiligo was evaluated 6 months after treatment. Treatment responses were defined according to the extent of repigmentation as effective (if 50% or more repigmentation was achieved) or ineffective (if less than 50% or worse repigmentation was achieved). Patients received re-transplantation if the initial treatment was ineffective. The levels of C-X-C motif chemokine ligand (CXCL)9 and CXCL10 in blister fluid samples were significantly lower in stable patients than in active participants. Receiver operating characteristic analysis revealed that the levels of CXCL9 and CXCL10 were sensitive and specific in diagnosing active vitiligo. Further, 65.6% (21/32) of patients who received CMT had effective treatment responses. The high CXCL9 level in the blister fluid was a significant predictor of ineffective treatment responses. The treatment response was significantly enhanced after treatment. Four patients with ineffective treatment responses received anti-inflammatory treatment and re-transplantation. The CXCL9 and CXCL10 levels in the blister fluid were related to the presence of active vitiligo. Also, the CXCL9 level was a predictor of the effectiveness of CMT in treating vitiligo.

Detectability of Fibrils by Dilation Technique in Digital Mammography

The detectability of fibrils in mammographic phantom images by morphological enhancement was analysed in the present study. Materials that mimic fibrils were imaged by a digital mammography machine at 28 and 29 kVP. The images were processed by a dilation technique to produce second set of images. Receiver operating characteristic analysis was performed to compare the detection performance from the two sets of images. As compared to original images, the 28 kVP’s fibrils images from dilation technique become more prominence to be detected by observers. While at 29 kVP only a few observers can found the fibrils images from dilation technique. This study suggests morphological enhancement of mammography image did not increase the detection of low frequency signals of the images.

A-39 New Cut-Score to Improve Performance of the Memory Validity Profile (MVP) in Heterogenous Clinical Populations

Objective The Memory Validity Profile (MVP) is a standalone performance validity test developed specifically for use with children. Prior research has demonstrated the MVP’s strength in its ease of administration to children with a wide range of intellectual abilities. However, it has been found to lack sensitivity in detecting noncredible performance in select clinical populations using published cut-offs. The current study examines the MVP’s performance in a diagnostically heterogeneous clinical sample and proposes a new cut-off for optimization of sensitivity and specificity. Method Archival clinical data was examined from 96 participants referred for a comprehensive neuropsychological evaluation (ages 6–18). Receiver operating characteristic analysis was used to assess the discriminative ability of MVP in detecting cases of noncredible performance defined as failures on both the Test of Memory Malingering and Reliable Digit Span. Results Using published cut-offs, the MVP demonstrated perfect specificity (100%) but suboptimal sensitivity (33.3%). Receiver operating characteristic analysis revealed strong discrimination using MVP Total score (AUC = 0.891 (p < 0.001) and a MVP Total cut-score of ≤30 resulted in optimal sensitivity (89%) and specificity (63%). Conclusions Our findings provide additional evidence that published MVP cut-offs may be too lenient to adequately capture instances of noncredible performance and indicate an MVP Total score cut-off of ≤30 may be more appropriate for use with heterogeneous clinical populations.

Application of Lyon Consensus criteria for GORD diagnosis: evaluation of conventional and new impedance-pH parameters

ObjectiveTo validate Lyon Consensus criteria for diagnosing gastro-oesophageal reflux disease (GORD) by reflux monitoring.DesignManual review of impedance-pH tracings from patients with proton pump inhibitor (PPI)-dependent heartburn, evaluated off PPI. Acid exposure time (AET) thresholds defined by the Lyon Consensus and impedance parameters were investigated, namely, total refluxes (TRs), postreflux swallow-induced peristaltic wave (PSPW) index and mean nocturnal baseline impedance (MNBI).ResultsThe study included 488 patients, 178 (36%) with normal (<4%) AET, 89 (18%) with inconclusive (4%–6%) AET and 221 (45%) with abnormal (>6%) AET, alongside with 70 healthy controls. At receiver operating characteristic analysis, area under curve was 0.89, 0.95 and 0.89 for TRs, PSPW index and MNBI, respectively, and threshold values were 40, 50% and 2000 Ω; the 4% physiological AET threshold defined by the Lyon Consensus showed 100% specificity but 63% sensitivity. The thresholds defined for impedance parameters were validated against AET by means of ordered logistic regression, being in concordance with the 4% AET threshold (OR 2.5 for TRs, 18.9 for PSPW index and 5.7 for MNBI). TRs positivity and concordant PSPW index/MNBI positivity were found in 80%–90% of patients in the abnormal AET group, in 73%–74% of cases in the inconclusive AET group and in 28%–40% of cases in the group with normal AET.ConclusionsOur results show the overall validity of the Lyon Consensus approach to GORD diagnosis. Adding evaluation of impedance parameters, namely, TRs, PSPW index and MNBI to AET appraisal, substantially improves the diagnostic yield of reflux monitoring.

Impact of modified albumin–bilirubin grade on survival in patients with HCC who received lenvatinib

We investigated the impact on survival of modified albumin–bilirubin (mALBI) grade versus Child–Pugh classification in patients with hepatocellular carcinoma (HCC) who received lenvatinib. A total of 524 patients with HCC who received lenvatinib were included. Univariate analysis showed that mALBI grade 2b/3 and Child–Pugh class B/C were significantly associated with survival [hazard ratio (HR), 2.471; 95% confidence interval (CI), 1.944–3.141 and HR, 2.178; 95%CI, 1.591–2.982]. In patients with a Child–Pugh score of 5, multivariate analysis showed that mALBI grade 2b/3 was independently associated with survival (HR, 1.814; 95%CI, 1.083–3.037). Conversely, among patients with mALBI grade 1/2a, there was no difference in survival between those with a Child–Pugh class of 5 or 6 (p = 0.735). Time-dependent receiver operating characteristic analysis showed that the ALBI score predicted survival better than the Child–Pugh score. The optimal cut-off value of the ALBI score for predicting survival was nearly the same as the value separating mALBI grades 2a and 2b. In conclusion, the mALBI grade was a better predictor of survival than the Child–Pugh classification in patients with unresectable HCC who received lenvatinib therapy.

Can neutrophil-to-lymphocyte ratio be used as a predictor in acute appendicitis?

Background: To determine if neutrophil-to-lymphocyte ratio (NLR) can be used to diagnose appendicitis and distinguish complicated from uncomplicated appendicitis. The secondary aim was to determine if the appendix cut-off size on ultrasound matches that of existing literature. Methods: We retrospectively analyzed all cases that underwent appendectomy in Father Muller medical college and hospital from 2014 to 2019. The NLR, histopathology, and ultrasound reports for all patients were reviewed. Recommended cut-off values for NLR and appendicular size on ultrasound were determined using receiver operating characteristic analysis (ROC). Data was analyzed using SPSS version 25. Ethical approval was obtained for this study. Results: We included 1623 patients in this study. The patients’ median age was 24 years, with appendicitis being more common in males than females. NLR>2.4 was statistically associated with appendicitis with sensitivity of 70.1% and specificity of 43.2%. NLR>4.3 was statistically associated with complicated appendicitis with sensitivity of 72.25% and specificity of 54.09%. An appendicular diameter >6.1 mm was suggestive of appendicitis on abdominal ultrasound based on our analysis. Conclusions: NLR is a simple adjunct that can be used to diagnose appendicitis and identify complicated appendicitis.

Impact of Modified Albumin–Bilirubin Grade on Survival in Patients With HCC Who Received Lenvatinib: An Analysis Using Time-Dependent ROC

We investigated the impact on survival of modified albumin–bilirubin (mALBI) grade vs. Child–Pugh classification in patients with hepatocellular carcinoma (HCC) who received lenvatinib. A total of 524 patients with HCC who received lenvatinib were included. Univariate analysis showed that mALBI grade 2b/3 and Child–Pugh class B/C were significantly associated with survival (hazard ratio [HR], 2.471; 95% confidence interval [CI], 1.944–3.141 and HR, 2.178; 95%CI, 1.591–2.982). In patients with a Child–Pugh score of 5, multivariate analysis showed that mALBI grade 2b/3 was independently associated with survival (HR, 1.814; 95%CI, 1.083–3.037). Conversely, among patients with mALBI grade 1/2a, there was no difference in survival between those with a Child–Pugh class of 5 or 6 (p = 0.735). Time-dependent receiver operating characteristic analysis showed that the ALBI score predicted survival better than the Child–Pugh score. The optimal cut-off value of the ALBI score for predicting survival was nearly the same as the value separating mALBI grades 2a and 2b. In conclusion, the mALBI grade was a better predictor of survival than the Child–Pugh classification in patients with unresectable HCC who received lenvatinib therapy.