Factors associated with weak positive SARS-CoV-2 diagnosis by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR)

During the COVID-19 pandemic, the reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) assay has been the primary method of diagnosis of SARS-CoV-2 infection. However, RT-qPCR assay interpretation can be ambiguous with no universal absolute cut-off value to determine sample positivity, which particularly complicates the analysis of samples with high Ct values, or weak positives. Therefore, we sought to analyse factors associated with weak positive SARS-CoV-2 diagnosis.

We analysed sample data associated with all positive SARS-CoV-2 RT-qPCR diagnostic tests performed by the Victorian Infectious Diseases Reference Laboratory (VIDRL) in Melbourne, Australia, during the Victorian first wave (22 January 2020–30 May 2020). A subset of samples was screened for the presence of host DNA and RNA using qPCR assays for CCR5 and 18S, respectively.

Assays targeting the viral RNA-dependent RNA polymerase (RdRp) had higher Ct values than assays targeting the viral N and E genes. Weak positives were not associated with the age or sex of individuals’ samples nor with reduced levels of host DNA and RNA. We observed a relationship between Ct value and time post-SARS-CoV-2 diagnosis.

High Ct value or weak positive SARS-CoV-2 was not associated with any particular bias including poor biological sampling.

Novel technique of sutureless glueless scleral fixated intraocular lens (SFIOL)

Purpose:

To report results of a novel technique for sutureless, glueless intrascleral fixation of three-piece posterior chamber intraocular lens (IOL) using 26-G needle for management of aphakia.

Methods:

In this prospective series, 30 eyes of 20 patients with aphakia, subluxated IOL, or crystalline lens were included. 26-G-needle-guided intrascleral fixation of three-piece posterior chamber IOL was performed according to the described technique. The patients were evaluated on day 2, 1 week, 6 weeks, and 3 months postoperatively for change in best-corrected visual acuity (BCVA), intraocular pressure (IOP), IOL centration, and any other complications. The postoperative tilt of the IOL was indirectly measured by determining the lenticular astigmatism which in turn was calculated by the difference between net corneal astigmatism and refractive astigmatism. Paired t-test was used to determine the significance of any association between the preoperative and postoperative BCVA and IOP. P < 0.05 was considered significant.

Results:

Of 30 eyes (n = 30 patients), 18 were surgical aphakia, 6 traumatic aphakia, 5 subluxated IOL, and 1 ectopia lentis (Marfan syndrome). The mean preoperative BCVA was 1.37 ± 0.37 (logMAR) and postoperative BCVA at 3 months was 0.37 ± 0.29 (logMAR). A significant improvement in the mean BCVA (P < 0.05) was observed after the procedure. The mean IOP preoperatively was 13.33 ± 4.18 and postoperatively at 3 months was 12.82 ± 3.97 (P > 0.05), which was not significant. None of the eyes developed any intraoperative and postoperative complications. The IOLs had appropriate centration and stability.

Conclusion:

We have developed this new technique for intrascleral IOL fixation which is quite simple, cost-effective, minimally invasive, neither requires glue nor suture and gives consistent outcome.

A naturally occurring rare analog of quercetin promotes peak bone mass achievement and exerts anabolic effect on osteoporotic bone

The effect of quercetin C-glucoside (QCG) on osteoblast function in vitro and bone formation in vivo was investigated. QCG supplementation promoted peak bone mass achievement in growing rats and new bone formation in osteopenic rats. QCG has substantial oral bioavailability. Findings suggest a significant bone anabolic effect of QCG.

INTRODUCTION

Recently, we showed that extracts of Ulmus wallichiana promoted peak bone mass achievement in growing rats and preserved trabecular bone mass and cortical bone strength in ovariectomized (OVx) rats. 3,3',4',5,7-Pentahydroxyflavone-6-C-β-D-glucopyranoside, a QCG, is the most abundant bioactive compound of U. wallichiana extract. We hypothesize that QCG exerts bone anabolic effects by stimulating osteoblast function.

METHODS

Osteoblast cultures were harvested from rat calvaria and bone marrow (BM) to study differentiation and mineralization. In vivo, growing female Sprague Dawley rats and OVx rats with osteopenia were administered QCG (5.0 or 10.0 mg kg(-1) day(-1)) orally for 12 weeks. Efficacy was evaluated by examining changes in bone microarchitecture using histomorphometric and microcomputed tomographic analyses and by determination of new bone formation by fluorescent labeling of bone. Plasma and BM levels of QCG were determined by high-performance liquid chromatography.

RESULTS

QCG was much more potent than quercetin (Q) in stimulating osteoblast differentiation, and the effect of QCG was not mediated by estrogen receptors. In growing rats, QCG increased BM osteoprogenitors, bone mineral density, bone formation rate, and cortical deposition. In osteopenic rats, QCG treatment increased bone formation rate and improved trabecular microarchitecture. Comparison with the sham group (ovary intact) revealed significant restoration of trabecular bone in osteopenic rats treated with QCG. QCG levels in the BM were ~50% of that of the plasma levels.

CONCLUSION

QCG stimulated modeling-directed bone accrual and exerted anabolic effects on osteopenic rats by direct stimulatory effect on osteoprogenitors likely due to substantial QCG delivery at tissue level following oral administration.