Practical considerations to establish a validated platform for pooled detection of SARS-CoV-2 by droplet digital PCR

Detection of SARS-CoV-2 has created an enormous workload for laboratories worldwide resulting in a restriction at the time of massive testing. Pool testing is a strategy that reduces time and costs. However, beyond the detection of infectious diseases in blood banks, this approach is rarely implemented in routine laboratories. Therefore, what was learned from the SARS-CoV-2 pool testing should represent an opportunity to increase diagnostic capabilities. The present work, carried out in the context of a diagnostic laboratory of a public hospital during the COVID-19 pandemic, represents a contribution to this end. The main limitation of pool testing is the risk of false negatives that could have been identified by individual tests. These limitations are the dilution of samples with a low virus load during pooling and that the integrity of the sample may be affected by the quality of the sample collection. Fortunately, both limitations coincide with the main strengths of droplet digital PCR (ddPCR). ddPCR is a third-generation PCR that splits the amplification into thousands of droplets that work in parallel, increasing sensitivity and resistance to inhibitors. Therefore, ddPCR is particularly useful for pool testing. Here we show how to factor between test sensitivity and savings in test time and resources. We have identified and optimized critical parameters for pool testing. The present study, which analyzed 1000 nasopharyngeal samples, showed that the pool testing could detect even a single positive sample with a CT value of up to 30 in pools of 34 samples. This test was performed using three different standard extraction methods, the simplest being heating only, which resulted in substantial savings of extraction reagents in addition to PCR reagents. Moreover, we show that pooling can be extended to use saliva, which is less invasive and allows self-collection, reducing the risk for health personnel.

CNBP controls transcription by unfolding DNA G-quadruplex structures

Guanine-rich DNA strands can fold into non-canonical four-stranded secondary structures named G-quadruplexes (G4). Experimental evidences suggest that G4-DNA surrounding transcription start sites act as cis-regulatory elements by either stimulating or inhibiting gene transcription. Therefore, proteins able to target and regulate specific G4 formation/unfolding are crucial for G4-mediated transcriptional control. Here we present data revealing that CNBP acts in vitro as a G4-unfolding protein over a tetramolecular G4 formed by the TG₄T oligonucleotide, as well as over the G4 folded in the promoters of several oncogenes. CNBP depletion in cellulo led to a reduction in the transcription of endogenous KRAS, suggesting a regulatory role of CNBP in relieving the transcriptional abrogation due to G4 formation. CNBP activity was also assayed over the evolutionary conserved G4 enhancing the transcription of NOGGIN (NOG) developmental gene. CNBP unfolded in vitro NOG G4 and experiments performed in cellulo and in vivo in developing zebrafish showed a repressive role of CNBP on the transcription of this gene by G4 unwinding. Our results shed light on the mechanisms underlying CNBP way of action, as well as reinforce the notion about the existence and function of G4s in whole living organisms.

[What influences reconvalescence after lung resection?]

INTRODUCTION

Reconvalescence after lung resections underlies several influences. The aim of this study was to outline the effect of patient and operative factors.

METHODS

Between 1/97 and 6/98 a cross sectional prospective study was undertaken at the University of Ulm. 125 patients with lung resections for various reasons via anterolateral thoracotomy were included. Variants thought to affect postoperative recovery were statistically analysed using uni- and multivariate analysis. A "good postoperative recovery" (GPR) was seen as at least two of the following criteria were fulfilled on the second postoperative day: Spitzer Index >/=6, FEV1 >40% of preoperative measurement, pain on LASA scale </=3.

RESULTS

Chi-Square testing revealed a more frequent GPR for patients with benign diseases (61 vs 40%, p=0,0436), an atypical compared to anatomical resection (63 vs 40%, p=0,0157) and an opening of the retractor of not more than 13 cm (61 vs 34%, p=0,0033). Multivariate analysis demonstrated only the opening of the retractor as being of independent influence (p=0,0148). Age, sex, BMI, incision length, transsection of M. latissimus dorsi, number of accidental rib fractures, time of operation and routine of the surgeon were of no statistical relevance to GPR.

DISCUSSION

Malignant disease requiring anatomical lung resection is accompanied by delayed postoperative recovery when compared to lung resections for other reason. In contrast the width of opening of the retractor is of independent negative influence for reconvalescence. Once more the significance of a non-aggressive access procedure for lung resections is underlined.

In utero fetal muscle biopsy: a precious aid for the prenatal diagnosis of Duchenne muscular dystrophy

Prenatal diagnosis for Duchenne muscular dystrophy can usually be performed using DNA analysis. This approach would be impossible when there is only one prior affected male and no identifiable gene deletion. Therefore, in utero fetal thigh muscle biopsy with direct examination of muscle by dystrophin analysis may provide the only means of prenatal diagnosis. We report such a case in which fetal muscle biopsy was able to exclude Duchenne muscular dystrophy. A detailed literature review of the topic is provided.

Diagnosis and successful in utero treatment of a fetal goitrous hyperthyroidism caused by maternal Graves' disease. A case report

A case of maternal treated Graves' disease associated with hyperthyroid fetal goiter is presented. Fetal goiter is diagnosed by ultrasound and hyperthyroidism is confirmed by fetal blood sampling. Fetal thyroid status is normalized by maternal carbamizole treatment whereas the mother is euthyroid with replacement therapy after subtotal thyroidectomy. Repeated funipuncture allows us to adjust the fetal treatment. The infant is euthyroid at birth. Pathogenesis, diagnosis and treatment of fetal thyrotoxicosis complicated with maternal Graves' disease are discussed.

Prenatal diagnosis of a congenital astrocytoma: a case report and literature review

Congenital intracranial tumors are very rare. We report an endovaginal ultrasonographic diagnosis of an anaplastic astrocytoma at 31 weeks' gestation. Other means, such as antenatal magnetic resonance imaging and fetal blood sampling were not shown to have any diagnostic advantage. A detailed literature review of the topic is provided.

[The Infraguide system in laparoscopic surgery]

Infraguide is a system to transmit laser beams into the abdominal cavity through multiple reflexions in a hollow tube of ceramic mirror. The latter is protected by a metal tube of 3 mm outside diameter. After an experience of 45 cases, the authors analyse the advantages and the disadvantages of this system. The advantages are: the manageability, the small diameter, the excellent visibility of the pilot beam and the easy evacuation of the smoke. The disadvantage is minor: the focused spot cannot be smaller than 0.78 mm.

[Rupture of an unscarred uterus at full term after an intracervical application of dinoprostone (Prepidil) gel]

The authors report a case of uterine rupture following intra-cervical application of dinoprostone (two doses at an interval of 6 hours). No oxytocic had been administered and recording of the contractions had revealed no hyperkinesia or hypertonia one hour before rupture occurred.