Test, trace, isolate: evidence for declining SARS-CoV-2 PCR sensitivity in a clinical cohort.

Real-time reverse transcription-polymerase chain reaction (RT-PCR) on upper respiratory tract (URT) samples is the primary method to diagnose SARS-CoV-2 infections and guide public health measures, with a supportive role for serology. We reinforce previous findings on limited sensitivity of PCR testing, and solidify this fact by statistically utilizing a firm basis of multiple tests per individual. We integrate stratifications with respect to several patient characteristics such as severity of disease and time since onset of symptoms. Bayesian statistical modelling was used to retrospectively determine the sensitivity of RT-PCR using SARS-CoV-2 serology in 644 COVID-19-suspected patients with varying degrees of disease severity and duration. The sensitivity of RT-PCR ranged between 80% - 95%; increasing with disease severity, it decreased rapidly over time in mild COVID-19 cases. Negative URT RT-PCR results should be interpreted in the context of clinical characteristics, especially with regard to containment of viral transmission based on 'test, trace and isolate'. Keywords: SARS-CoV-2, RT-PCR, serology, sensitivity, public health.

Rapid identification of SARS-CoV-2-infected patients at the emergency department using routine testing.

Objectives: The novel coronavirus disease 19 (COVID-19), caused by SARS-CoV-2, spreads rapidly across the world. The exponential increase in the number of cases has resulted in overcrowding of emergency departments (ED). Detection of SARS-CoV-2 is based on an RT-PCR of nasopharyngeal swab material. However, RT-PCR testing is time-consuming and many hospitals deal with a shortage of testing materials. Therefore, we aimed to develop an algorithm to rapidly evaluate an individual's risk of SARS-CoV-2 infection at the ED. Methods: In this multicenter retrospective study, routine laboratory parameters (C-reactive protein, lactate dehydrogenase, ferritin, absolute neutrophil and lymphocyte counts), demographic data and the chest X-ray/CT result from 967 patients entering the ED with respiratory symptoms were collected. Using these parameters, an easy-to-use point-based algorithm, called the corona-score, was developed to discriminate between patients that tested positive for SARS-CoV-2 by RT-PCR and those testing negative. Computational sampling was used to optimize the corona-score. Validation of the model was performed using data from 592 patients. Results: The corona-score model yielded an area under the receiver operating characteristic curve of 0.91 in the validation population. Patients testing negative for SARS-CoV-2 showed a median corona-score of 3 vs. 11 (scale 0-14) in patients testing positive for SARS-CoV-2 (p<0.001). Using cut-off values of 4 and 11 the model has a sensitivity and specificity of 96 and 95%, respectively. Conclusions: The corona-score effectively predicts SARS-CoV-2 RT-PCR outcome based on routine parameters. This algorithm provides the means for medical professionals to rapidly evaluate SARS-CoV-2 infection status of patients presenting at the ED with respiratory symptoms.

Intrinsic abnormalities of lymphocyte counts in children with down syndrome.

OBJECTIVE: Down syndrome (DS) is associated with an increased frequency of infections, hematologic malignancies, and autoimmune diseases, suggesting that immunodeficiency is an integral part of DS that contributes significantly to the observed increased morbidity and mortality. We determined the absolute counts of the main lymphocyte populations in a large group of DS children to gain further insight into this immunodeficiency. STUDY DESIGN: In a large group of children with DS (n = 96), the absolute numbers of the main lymphocyte subpopulations were determined with 3-color immunophenotyping using the lysed whole-blood method. The results were compared with previously published data in healthy children without DS. RESULTS: In healthy children with DS, the primary expansion of T and B lymphocytes seen in healthy children without DS in the first years of life was severely abrogated. The T- lymphocyte subpopulation counts gradually reached more normal levels with time, whereas the B- lymphocyte population remained severely decreased, with 88% of values falling below the 10th percentile and 61% below the 5th percentile of normal. CONCLUSIONS: The diminished expansion of T and B lymphocytes strongly suggests that a disturbance in the adaptive immune system is intrinsically present in DS and is not a reflection of precocious aging. Thymic alterations have been described in DS that could explain the decreased numbers of T lymphocytes, but not the striking B lymphocytopenia, seen in these children.

Evidence for increased oxidative stress in peroxisomal D-bifunctional protein deficiency.

Peroxisome biogenesis disorders (PBDs) and D-bifunctional protein (D-BP) deficiency are two types of inherited peroxisomal disorders. Patients with a PBD lack functional peroxisomes and patients with D-BP deficiency lack the enzyme, which is responsible for the second and third step of the peroxisomal beta-oxidation. The clinical presentation of these peroxisomal disorders is severe and includes several neurological abnormalities. The pathological mechanisms underlying these disorders are not understood and no therapies are available. Because peroxisomes have been associated with oxidative stress, as oxygen radicals are both produced and scavenged in peroxisomes, we have investigated whether oxidative stress is involved in the pathogenesis of PBDs and D-BP deficiency. We found in D-BP-deficient patients increased levels of thiobarbituric acid-reactive substances (TBARS) and 8-hydroxydeoxyguanosine (8-OHdG), which are markers for lipid peroxidation and oxidative DNA damage, respectively, whereas the levels of the lipophilic antioxidants alpha-tocopherol and coenzyme Q(10) were decreased. In addition, we found in skin fibroblasts from D-BP-deficient patients an imbalance between the activities of the peroxisomal H(2)O(2)-generating straight-chain acyl-CoA oxidase (SCOX) and the peroxisomal H(2)O(2)-degrading enzyme catalase. In conclusion, we have found clear evidence for the presence of increased oxidative stress in patients with D-BP deficiency, but not in patients with a PBD.