Clipped Axillary Node as a Potential Surrogate for Overall Axillary Nodal Status in Inflammatory Breast Cancer Patients after Neoadjuvant Chemotherapy.

BACKGROUND: Axillary lymph node dissection is the current standard for management of the axilla in inflammatory breast cancer (IBC). The present study aims to determine whether the initially positive node identified by clip placement accurately represents the overall nodal status of axilla after neoadjuvant chemotherapy (NAC) in IBC. PATIENTS AND METHODS: A retrospective study was conducted on patients with IBC who underwent operation (2014-2023). For patients with IBC who had clip placement in a positive axillary node at diagnosis, operative notes, specimen radiographs, and pathology reports were reviewed to confirm final pathologic status of clipped nodes. RESULTS: In total, 92 patients with IBC (90 cN+) were identified (median age 54 years, 78% invasive ductal, 10% invasive lobular, and 12% mixed); 81 (90%) were biopsy-proven cN+, with a clip placed in the positive node for 62/81 (77%). All patients were treated with NAC and axillary surgery with median 19 (range 4-49) nodes removed. Among 28 (out of 56) patients with retrieved clipped nodes that were pathologically negative (ypN0), only 1 had an additional positive node with micrometastasis for a false negative rate of 4% (95% CI 1-19%). Conversely, 3/3 patients with isolated tumor cells (ITCs) only in the clipped node had additional axillary disease (ITCs in 1, macrometastasis in 2), and 20/23 (87%) of patients with pathologically positive clipped node (micrometastasis or greater) had additional positive nodes [19/20 (95%) with macrometastasis]. CONCLUSIONS: The clipped biopsy-positive axillary node in IBC accurately represented the post-NAC overall axillary nodal status. ITCs post-NAC should be considered positive as an indicator of additional nodes with metastasis.

Clinical Outcomes of Benign Concordant MRI-Guided Breast Biopsies.

INTRODUCTION: MRI-guided biopsy is the standard of care for breast imaging findings seen only by MRI. Although a non-zero false-negative rate of MRI-guided breast biopsy has been reported by multiple studies, there are varied practice patterns for imaging follow-up after a benign concordant MRI guided biopsy. This study assessed the outcomes of benign concordant MRI-guided biopsies at a single institution. PATIENTS AND METHODS: This IRB-approved, retrospective study included patients with MRI-guided biopsies of breast lesions from November 1, 2014, to August 31, 2020. Only image-concordant breast lesions with benign histopathology and those follow up with MRI imaging or excision were included in the study. RESULTS: Out of 275 lesions in 216 patients that met the inclusion criteria, 274 lesions were followed with MRI (range, 5-79 months; average, 25.5 months) and showed benign or stable features upon follow-up. One out of 275 lesions (0.4%), a 6 mm focal nonmass enhancement, was ultimately found to represent malignancy after initial MRI-guided biopsy yielded fibrocystic changes. The lesion was stable at a 6-month follow-up MRI but increased in size at 18 months. Repeat biopsy by ultrasound guidance yielded invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS). CONCLUSION: Breast MRI-guided biopsy has a low false-negative rate. Our single malignancy from a total of 275 lesions gives a false negative rate of 0.4%. This data also supports a longer follow-up interval than the commonly performed 6-month follow-up, in order to assess for interval change.

Accuracy of sentinel lymph node biopsy in male breast cancer: Systematic review and meta-analysis.

BACKGROUND: Sentinel lymph node biopsy (SLNB) is commonly used in the surgical management of male breast cancer. Contrary to female breast cancer, limited data exist about its performance in male breast cancer. The objective of this systematic review and meta-analysis was to evaluate the SLNB accuracy in male breast cancer. METHODS: MEDLINE, EMBASE, Web of Science and The Cochrane Library were searched from January 1995 to April 2023 for studies evaluating the SLNB identification rate and false-negative rate in male breast cancer with negative preoperative axillary evaluation and primary surgery. For SLNB false-negative rate, the gold standard was the histology of axillary lymph node dissection (ALDN). Methodological quality was assessed by using the QUADAS-2 tool. Pooled estimates of the SLNB identification rate and false-negative rate were calculated. Heterogeneity of the pooled studies was evaluated using I2 index. RESULTS: A total of 12 retrospective studies were included. The 12 studies that reported the SLNB identification rate gathered a total of 164 patients; the 5 studies that reported the SLNB false-negative rate gathered a total of 50 patients with a systematic ALND. The pooled estimate of the SLNB identification rate was 99.0%. The SLNB false-negative rates were 0% in the 5 included studies and consequently so as the pooled estimate of the false-negative rate with no heterogeneity. CONCLUSION: SLNB for male breast cancer, following negative preoperative axillary assessment and primary surgery, appears feasible, consistent, and effective. Our research supports conducting immediate SLNB histological evaluation to facilitate prompt ALND in case of positive results.

New EAU/ASCO guideline recommendations on sentinel node biopsy for penile cancer and remaining challenges from a nuclear medicine perspective.

INTRODUCTION: The European Association of Urology (EAU) and the American Society of Clinical Oncology (ASCO) recently issued updated guidelines on penile cancer, emphasising dynamic sentinel node biopsy (DSNB) as the preferred method for surgical staging among patients with invasive penile tumours and no palpable inguinal lymphadenopathy. This paper outlines the rationale behind this new recommendation and describes remaining challenges, as well as strategies for promoting DSNB worldwide. MAIN TEXT: DSNB offers high diagnostic accuracy with the lowest postoperative complications compared to open or minimally invasive inguinal lymph node dissection (ILND), prompting its preference in the new guidelines. Nevertheless, despite its advantages, there are challenges hampering the widespread adoption of DSNB. This includes the false-negative rate associated with DSNB and the potential negative impact on patient outcome. To address this issue, improvements should be made in several areas, including refining the timing and interpretation of the lymphoscintigraphy and the single photon emission computed tomography/computed tomography images. In addition, the quantity of tracer employed and choice of the injection site for the radiopharmaceutical should be optimised. Finally, limiting the removal of nodes without tracer activity during surgery may help minimise complication rates. CONCLUSION: Over the years, DSNB has evolved significantly, related to the dedicated efforts and innovations in nuclear medicine and subsequent clinical studies validating its efficacy. It is now strongly recommended for surgical staging among selected penile cancer patients. To optimise DSNB further, multidisciplinary collaborative research is required to improve SN identification for better diagnostic accuracy and fewer complications.

Effectiveness of R1-nj Anthocyanin Marker in the Identification of In Vivo Induced Maize Haploid Embryos.

Doubled haploid (DH) technology has become integral to maize breeding programs to expedite inbred line development and increase the efficiency of breeding operations. Unlike many other plant species that use in vitro methods, DH production in maize uses a relatively simple and efficient in vivo haploid induction method. However, it takes two complete crop cycles for DH line generation, one for haploid induction and the other one for chromosome doubling and seed production. Rescuing in vivo induced haploid embryos has the potential to reduce the time for DH line development and improve the efficiency of DH line production. However, the identification of a few haploid embryos (~10%) resulting from an induction cross from the rest of the diploid embryos is a challenge. In this study, we demonstrated that an anthocyanin marker, namely R1-nj, which is integrated into most haploid inducers, can aid in distinguishing haploid and diploid embryos. Further, we tested conditions that enhance R1-nj anthocyanin marker expression in embryos and found that light and sucrose enhance anthocyanin expression, while phosphorous deprivation in the media had no affect. Validating the use of the R1-nj marker for haploid and diploid embryo identification using a gold standard classification based on visual differences among haploids and diploids for characteristics such as seedling vigor, erectness of leaves, tassel fertility, etc., indicated that the R1-nj marker could lead to significantly high false positives, necessitating the use of additional markers for increased accuracy and reliability of haploid embryo identification.

Benign cytology does not rule out malignancy in thyroid nodules larger than 4 cm.

BACKGROUND: For thyroid nodules ≥4 cm, the accuracy of fine-needle aspiration biopsy (FNAB) is controversial and the approach is unclear. We aimed to compare FNAB and operation of thyroid nodules and to determine the accuracy of FNAB. MATERIAL AND METHODS: All total thyroidectomies performed between January 2015 and December 2021 were evaluated. In the study, 301 patients were included. Euthyroid patients with preoperative thyroid ultrasound, FNAB results and operation results were recorded retrospectively. RESULTS: The nodule size was <4 cm in 79.1% of the patients, and ≥4 cm in 20.9%. In patients with nodule size ≥4 cm, 50.8% of FNAB results were reported as benign, and 43.7% of these patients were found to be malignant at the end of the operation. In nodules <4 cm, 36.8% of the patients whose FNAB results were found to be benign were malignant. False-negativity rate was found to be quite high in ≥4 cm nodules. CONCLUSIONS: For thyroid nodules, diagnostic lobectomy may be necessary because the false-negative rate of FNAB was high, especially in nodules ≥4 cm. In addition, intermediate results, such as AUS/FN, have a higher risk of malignancy in nodules of ≥4 cm compared to nodules of <4 cm.

False Negative Rate of Sentinel Lymph Node Biopsy on Intraoperative Frozen Section in Early Breast Cancer Patients: An Institutional Experience.

Sentinel lymph node biopsy is an established practice to avoid axillary clearance, in clinically negative axilla, in breast cancer patients. Sentinel nodes harvested by dual technique, if found negative on intraoperative frozen section, can prevent breast cancer patient from a potentially debilitating complete axillary clearance. Hence, analyzing the institutional accuracy of this technique and comparing it with international standards, becomes important in providing optimal treatment to these patients. A retrospective analysis of all patients who had undergone sentinel lymph node biopsy at our institute from December 2014 to December 2018 was carried out. At our institute, sentinel lymph nodes are identified using dual technique of methylene blue and radiocolloid dye. Intraoperative frozen section of these hot or blue or any enlarged nodes is performed. Patients with positive frozen section undergo complete axillary clearance. All frozen and unfrozen biopsy material is subjected to further paraffin sectioning and immunohistochemistry. False negative rate and factors associated with were analyzed. A total number of 424 patients had undergone intraoperative frozen section for the sentinel node in breast cancer at our institute during the study period. Among these, 307 patients had negative sentinel nodes and 117 had positive sentinel nodes of frozen section. Seventeen patients out of 307 had lymph node metastases in final paraffin report (false negative rate = 12.6%). Two of these were found to have macrometastasis, 13 had micrometastasis and 2 had isolated tumor cells on final immunohistochemistry report. Size of metastases to sentinel lymph node was found to be a statistically significant contributor to higher false negative rate. Sentinel lymph node biopsy using intraoperative frozen section, is a sensitive and specific technique of staging axilla in breast cancer patients. Detection of micrometastasis and isolated tumor cells present a technical challenge and are associated with higher false negative rates.

Interest of para-aortic lymphadenectomy for locally advanced cervical cancer in the era of PET scanning.

BACKGROUND AND OBJECTIVES: Treatment of locally advanced cervical cancer (LACC) involves pelvic chemoradiotherapy, using an extended field in the case of para-aortic involvement. 18-Fluoro-D-glucose positron emission tomography combined with computer tomography (PET-CT) is an accurate method for the detection of metastatic nodes. The objective of this study was to evaluate the performance of PET-CT for lymph node staging of LACC. METHODS: This bicentric retrospective study included patients with LACC who had a PET-CT scan followed by para-aortic lymphadenectomy between January 2015 and December 2019. Based on pathological findings, sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) and false-negative (FN) rates of PET-CT for para-aortic node involvement were evaluated. RESULTS: Seventy-one patients who had undergone laparoscopic lymphadenectomy were included in this study. The intraoperative complication rate was 2.8%. Sensitivity, specificity, NPV and PPV for PET-CT were 55% [95% confidence interval (CI) 44.6-67.1], 84% (95% CI 75-92), 93% (95% CI 87-99) and 33% (95% CI 22-44), respectively. FN rates in the case of negative or positive pelvic PET-CT were 5.7% and 9.5%, respectively. CONCLUSIONS: Para-aortic lymphadenectomy is recommended for lymph node staging in the case of negative para-aortic PET-CT. In view of the low FN rate of PET-CT, surgical staging should be discussed regardless of pelvic status if the patient presents high surgical risk, or if this delays the commencement of chemoradiotherapy.

Diagnostic accuracy of axillary nodal ultrasound after neoadjuvant chemotherapy in node-positive breast cancer patients: A validation study.

OBJECTIVE: To determine the accuracy and false negative rate of axillary ultrasound compared to sentinel node biopsy. METHODS: The retrospective study was conducted at the Aga Khan University Hospital, Karachi, from February 1 to March 31, 2021, and comprised data of breast cancer patients who had undergone neo-adjuvant chemotherapy followed by axillary lymph node dissection or axillary disease diagnosed using lymph node biopsy or sentinel lymph node biopsy between January 1, 2016, and December 30, 2020. After receiving neoadjuvant chemotherapy, axillary ultrasound findings were compared with histopathology of lymph nodes. Data was analysed using SPSS 22. RESULTS: Of the 155 patients evaluated, 104(67.1%) were diagnosed with negative axillary lymph nodes and 51(32.9%) were diagnosed with positive axillary lymph nodes post-chemotherapy. The overall mean age was 51.13±1.3 years. When histopathology results were compared with those of axillary ultrasound, 36(23.2%) cases turned out to be true positive, while 23(14,8%) were false negative, yielding a positive predictive value of 75% and negative predictive value of 65%. Axillary ultrasound had 75% accuracy, false negative rate 30%, sensitivity 61% and specificity 84.4%. CONCLUSIONS: Axillary ultrasound was found to be fairly useful, but not completely reliable, in identifying positive lymph nodes.

The screening value of RT-LAMP and RT-PCR in the diagnosis of COVID-19: systematic review and meta-analysis.

The purpose of this systematic review is to evaluate the test accuracy of reverse-transcription loop-mediated isothermal amplification (RT-LAMP) and reverse transcription-PCR (RT-PCR) for the diagnosis of coronavirus disease 2019 (COVID-19). We comprehensively searched PUBMED, Web of Science, the Cochrane Library, the Chinese National Knowledge Infrastructure, and the Chinese Biomedical Literature Service System until September 1, 2021. We included clinical studies assessing the sensitivity and specificity of RT-PCR and RT-LAMP using respiratory samples. Thirty-three studies were included with 9360 suspected cases of SARS-CoV-2 infection. The RT-PCR or other comprehensive diagnostic method was defined as the reference method. The results showed that the overall pooled sensitivity of RT-PCR and RT-LAMP was 0.96 (95 % CI, 0.93-0.98) and 0.92 (95 % CI, 0.85-0.96), respectively. RT-PCR and RT-LAMP had a 0.06 (95 % CI, 0.04-0.08) and 0.12 (95 % CI, 0.06-0.16) false-negative rates (FNR), respectively. Moreover, subgroup analysis showed mixed sampling and multiple target gene diagnosis methods had better diagnostic value than single-site sampling and a single target gene. The sensitivity and FNR were also significantly affected by the reference method. Comparing RT-LAMP with established suboptimal RT-PCR may exaggerate the performance of RT-LAMP. RT-PCR and RT-LAMP showed high values in the diagnosis of COVID-19, but there was still a FNR of about 6%-12%.

False negatives of screening in large-scale population / 上海预防医学

ObjectiveTo explore the changing trend of negative predictive value and number of false negatives in screening tests under the condition of low infection rate of infectious diseases. MethodsAssuming that the population is 20 million， to calculate the negative predictive value， numbers of true negatives and false negatives of the combination of different sensitivity （75.0%， 80.0%， 85.0%， 90.0%， 95.0%， 99.0%） and specificity （90.0%， 95.0%， 99.0%， 99.9%） when the disease infection rate of the population is 0.10%， 1.0% and 5.0% respectively. ResultsWhen the population infection rate is 0.1%， with the screening test sensitivity ≥75.0% and specificity ≥90.0%， the number of true negatives in 20 million people is about 17.98‒19.96 million. When the sensitivity is 75.0%， the negative predictive value is 99.972%‒99.975%， and the number of false negatives is 5 000； When the sensitivity increases to 99.0%， the negative predictive value is 99.999%， and the number of false negatives decreases to 200. When the population infection rate is 1.0%， a screening test with sensitivity ≥75.0% and specificity ≥90.0% can detect about 17.82‒19.78 million true negatives in 20 million population. When the sensitivity is 75.0%， the negative predictive value is 99.720%‒99.748%， and the number of false negatives is 50 000； When the sensitivity increases to 99.0%， the negative predictive value increases to 99.990%， and the number of false negatives decreases to 2 000. When the population infection rate is 5.0%， with sensitivity ≥75.0% and specificity ≥90.0%， the number of true negatives in 20 million people is about 17.10‒18.98 million； when the sensitivity is 75.0%， the negative predictive value is 98.559%‒98.700%， and the number of false negatives can reach 250 000； When the sensitivity is 99.0%， the negative predictive value increases to 99.942%‒99.947%， and the number of false negatives decreases to 10 000. The lower the infection rate of the population， the fewer false negatives will appear in the screening. ConclusionThe number of false negatives in large-scale screenings increases exponentially with the increase of infection rate. Screenings should be carried out as early as possible in a pandemic of infectious diseases， so as to control the spread of the pandemic as soon as possible.

The sensitivity of SARS-CoV-2 antigen tests in the view of large-scale testing.

OBJECTIVES: Antigen tests have emerged as an alternative to SARS-CoV-2 diagnostic PCR, thought to be valuable especially for the screening of bigger communities. To check appropriateness of the antigen based testing, we determined sensitivity of two point-of-care antigen tests when applied to a cohort of COVID-19 symptomatic, COVID-19 asymptomatic and healthy persons. METHODS: We examined nasopharyngeal swabs with antigen test 1 (Panbio Covid-19 Ag Rapid Test, Abbott) and antigen test 2 (Standard F Covid-19 Ag FIA, SD Biosensor). An additional nasopharyngeal and oropharyngeal swab of the same individual was checked with PCR (Allplex SARS-nCoV-2, Seegene). Within a 4-day period in October 2020, we collected specimens from 591 subjects. Of them, 290 had COVID-19 associated symptoms. RESULTS: While PCR positivity was detected in 223 cases, antigen test 1 and antigen test 2 were found positive in 148 (sensitivity 0.664, 95%CI 0.599, 0.722) and 141 (sensitivity 0.623, 95%CI 0.558, 0.684) patients, respectively. When only symptomatic patients were analysed, sensitivity increased to 0.738 (95%CI 0.667, 0.799) for the antigen test 1 and to 0.685 (95%CI 0.611, 0.750) for the antigen test 2. The substantial drop in sensitivity to 12.9% (95%CI 0.067, 0.234) was observed for samples with the PCR threshold cycle above > 30. CONCLUSIONS: Low sensitivity of antigen tests leads to the considerable risk of false negativity. It is advisable to implement repeated testing with high enough frequency if the antigen test is used as a frontline screening tool, and to follow with PCR if it is applied to vulnerable populations.

Studying mutation rate evolution in primates-the effects of computational pipelines and parameter choices.

This commentary investigates the important role of computational pipeline and parameter choices in performing mutation rate estimation, using the recent article published in this journal by Bergeron et al. entitled "The germline mutational process in rhesus macaque and its implications for phylogenetic dating" as an illustrative example.

Effects of the number of removed lymph nodes on survival outcome in patients with sentinel node-negative breast cancer.

BACKGROUND: Sentinel lymph node biopsy is the gold standard surgical technique for axillary staging in patients with clinically node-negative. However, it is still uncertain what is the optimal number of sentinel lymph nodes (SLNs) to be removed to reduce the false-negative rate. The aim of this study was to investigate whether patients with a single negative SLN have a worse prognosis than those with two or more negative SLNs. METHODS: A retrospective review was conducted on a large series of SLN-negative breast cancer patients. Survival outcomes and regional recurrence rate were evaluated according to the number of removed SLNs. Secondly, the contribution of different adjuvant therapies on disease-free survival was explored. Statistical analysis included the chi-square, Wilcoxon-Mann-Whitney test, and Kaplan-Meier survival analysis. RESULTS: A total of 1080 patients were included in the study. A first group consisted of 328 patients in whom a single SLN was retrieved, and a second group consisted of 752 patients in whom two or more SLNs were retrieved. There was no relevant difference in median DFS (64.9 vs 41.4) for SLN = 1 vs SLN > 1 groups (HR 0.76, CI 95% 0.39-1.46; p = 0.38). A statistically significant difference in mDFS was showed only for HT-treated patients who were SLN = 1 if compared to SLN > 1 (100.6 months versus 35.3 months). CONCLUSIONS: There is likely a relationship between the number of resected SNL and mDFS. Our results, however, showed no relevant difference in median DFS for SLN = 1 vs SLN > 1 group, except for a subset of the patients treated with hormone therapy.

[Atrial fibrillation diagnosis algorithm based on improved convolutional neural network].

Atrial fibrillation (AF) is a common arrhythmia, which can lead to thrombosis and increase the risk of a stroke or even death. In order to meet the need for a low false-negative rate (FNR) of the screening test in clinical application, a convolutional neural network with a low false-negative rate (LFNR-CNN) was proposed. Regularization coefficients were added to the cross-entropy loss function which could make the cost of positive and negative samples different, and the penalty for false negatives could be increased during network training. The inter-patient clinical database of 21 077 patients (CD-21077) collected from the large general hospital was used to verify the effectiveness of the proposed method. For the convolutional neural network (CNN) with the same structure, the improved loss function could reduce the FNR from 2.22% to 0.97% compared with the traditional cross-entropy loss function. The selected regularization coefficient could increase the sensitivity (SE) from 97.78% to 98.35%, and the accuracy (ACC) was 96.62%, which was an increase from 96.49%. The proposed algorithm can reduce the FNR without losing ACC, and reduce the possibility of missed diagnosis to avoid missing the best treatment period. Meanwhile, it provides a universal loss function for the clinical auxiliary diagnosis of other diseases.

The Guiding Significance of the Number of Positive Sentinel Lymph Nodes in Frozen Section for Intraoperative Axillary Dissection in Early Breast Cancer.

PURPOSE: The results of large randomised trials have changed the treatment strategy of axillary lymph nodes. Axillary lymph node dissection (ALND) can be avoided in some patients with one to two sentinel lymph nodes (SLNs) metastasis based on final paraffin section (FPS) results which called into question the need for intraoperative frozen section (FS). This study aims to assess the guiding value of the number of positive SLN detected via FS for intraoperative ALND. PATIENTS AND METHODS: This study retrospectively analyzed data from 3303 patients with breast cancer who underwent SLN biopsy between 2015 and 2019. Combined with the FPS results, FS sensitivity, specificity, and false negative rate (FNR) were calculated and the difference in the number of positive SLNs between FS and FPS was analyzed. RESULTS: The overall FNR of FS was 23.21%, which was 76.47% in isolated tumor cells, 62.28% in micrometastasis, and 12.09% in macrometastatic disease. The size of SLN metastasis were significantly associated with a higher FNR (p<0.001). The accuracy rate of the number of positive SLNs detected via FS was 92.62%. Human epidermal growth factor receptor 2 (HER2) (p<0.03) and Ki67 (p<0.02) were significant factors affecting the accuracy rate. CONCLUSION: FS is a effective method for SLN biopsy, ALND can be avoided in patients with one or two positive SLNs detected via FS.

Time variation in the probability of failing to detect a case of polymerase chain reaction testing for SARS-CoV-2 as estimated from a viral dynamics model.

Viral tests including polymerase chain reaction (PCR) tests are recommended to diagnose COVID-19 infection during the acute phase of infection. A test should have high sensitivity; however, the sensitivity of the PCR test is highly influenced by viral load, which changes over time. Because it is difficult to collect data before the onset of symptoms, the current literature on the sensitivity of the PCR test before symptom onset is limited. In this study, we used a viral dynamics model to track the probability of failing to detect a case of PCR testing over time, including the presymptomatic period. The model was parametrized by using longitudinal viral load data collected from 30 hospitalized patients. The probability of failing to detect a case decreased toward symptom onset, and the lowest probability was observed 2 days after symptom onset and increased afterwards. The probability on the day of symptom onset was 1.0% (95% CI: 0.5 to 1.9) and that 2 days before symptom onset was 60.2% (95% CI: 57.1 to 63.2). Our study suggests that the diagnosis of COVID-19 by PCR testing should be done carefully, especially when the test is performed before or way after symptom onset. Further study is needed of patient groups with potentially different viral dynamics, such as asymptomatic cases.

An Online Calculator to Better Understand the Impact of False-Negative COVID-19 Polymerase Chain Reaction Test Results in the Context of Anesthesia Providers.

What does the COVID-19 false-negative exposure problem mean in the context of a local anesthesia practice? We present a customizable online calculator designed to quantify and better understand individual and aggregate provider exposure risk.

False negative rate of COVID-19 PCR testing: a discordant testing analysis.

BACKGROUND: COVID-19 is diagnosed via detection of SARS-CoV-2 RNA using real time reverse-transcriptase polymerase chain reaction (rtRT-PCR). Performance of many SARS-CoV-2 rtRT-PCR assays is not entirely known due to the lack of a gold standard. We sought to evaluate the false negative rate (FNR) and sensitivity of our laboratory-developed SARS-CoV-2 rtRT-PCR targeting the envelope (E) and RNA-dependent RNA-polymerase (RdRp) genes. METHODS: SARS-CoV-2 rtRT-PCR results at the Public Health Laboratory (Alberta, Canada) from January 21 to April 18, 2020 were reviewed to identify patients with an initial negative rtRT-PCR followed by a positive result on repeat testing within 14 days (defined as discordant results). Negative samples from these discordant specimens were re-tested using three alternate rtRT-PCR assays (targeting the E gene and N1/N2 regions of the nucleocapsid genes) to assess for false negative (FN) results. RESULTS: During the time period specified, 95,919 patients (100,001 samples) were tested for SARS-CoV-2. Of these, 49 patients were found to have discordant results including 49 positive and 52 negative swabs. Repeat testing of 52 negative swabs found five FNs (from five separate patients). Assuming 100% specificity of the diagnostic assay, the FNR and sensitivity in this group of patients with discordant testing was 9.3% (95% CI 1.5-17.0%) and 90.7% (95% CI 82.6-98.9%) respectively. CONCLUSIONS: Studies to understand the FNR of routinely used assays are important to confirm adequate clinical performance. In this study, most FN results were due to low amounts of SARS-CoV-2 virus concentrations in patients with multiple specimens collected during different stages of infection. Post-test clinical evaluation of each patient is advised to ensure that rtRT-PCR results are not the only factor in excluding COVID-19.

Patterns of repeated diagnostic testing for COVID-19 in relation to patient characteristics and outcomes.

BACKGROUND: Whilst the COVID-19 diagnostic test has a high false-negative rate, not everyone initially negative is re-tested. Michigan Medicine, a primary regional centre, provided an ideal setting for studying testing patterns during the first wave of the pandemic. OBJECTIVES: To identify the characteristics of patients who underwent repeated testing for COVID-19 and determine if repeated testing was associated with downstream outcomes amongst positive cases. METHODS: Characteristics, test results, and health outcomes for patients presenting for a COVID-19 diagnostic test were collected. We examined whether patient characteristics differed with repeated testing and estimated a false-negative rate for the test. We then studied repeated testing patterns in patients with severe COVID-19-related outcomes. RESULTS: Patient age, sex, body mass index, neighbourhood poverty levels, pre-existing type 2 diabetes, circulatory, kidney, and liver diseases, and cough, fever/chills, and pain symptoms 14 days prior to a first test were associated with repeated testing. Amongst patients with a positive result, age (OR: 1.17; 95% CI: (1.05, 1.34)) and pre-existing kidney diseases (OR: 2.26; 95% CI: (1.41, 3.68)) remained significant. Hospitalization (OR: 7.88; 95% CI: (5.15, 12.26)) and ICU-level care (OR: 6.93; 95% CI: (4.44, 10.92)) were associated with repeated testing. The estimated false-negative rate was 23.8% (95% CI: (19.5%, 28.5%)). CONCLUSIONS: Whilst most patients were tested once and received a negative result, a meaningful subset underwent multiple rounds of testing. These results shed light on testing patterns and have important implications for understanding the variation of repeated testing results within and between patients.