Follow-Up SARS-CoV-2 PCR Testing Outcomes From a Large Reference Lab in the US.

By analyzing COVID-19 sequential COVID-19 test results of patients across the United States, we herein attempt to quantify some of the observations we've made around long-term infection (and false-positive rates), as well as provide observations on the uncertainty of sampling variability and other dynamics of COVID-19 infection in the United States. Retrospective cohort study of a registry of RT-PCR testing results for all patients tested at any of the reference labs operated by Labcorp® including both positive, negative, and inconclusive results, from March 1, 2020 to January 28, 2021, including patients from all 50 states and outlying US territories. The study included 22 million patients with RT-PCR qualitative test results for SARS-CoV-2, of which 3.9 million had more than one test at Labcorp. We observed a minuscule <0.1% basal positive rate for follow up tests >115 days, which could account for false positives, long-haulers, and/or reinfection but is indistinguishable in the data. In observing repeat-testing, for patients who have a second test after a first RT-PCR, 30% across the cohort tested negative on the second test. For patients who test positive first and subsequently negative within 96 h (40% of positive test results), 18% of tests will subsequently test positive within another 96-h span. For those who first test negative and then positive within 96 h (2.3% of negative tests), 56% will test negative after a third and subsequent 96-h period. The sudden changes in RT-PCR test results for SARS-CoV-2 from this large cohort study suggest that negative test results during active infection or exposure can change rapidly within just days or hours. We also demonstrate that there does not appear to be a basal false positive rate among patients who test positive >115 days after their first RT-PCR positive test while failing to observe any evidence of widespread reinfection.

A population-based analysis of the longevity of SARS-CoV-2 antibody seropositivity in the United States.

BACKGROUND: This cross-sectional study aimed to track population-based SARS-CoV-2 antibody seropositivity duration across the United States using observational data from a national clinical laboratory registry of patients tested by nucleic acid amplification (NAAT) and serologic assays. Knowledge of antibody seropositivity and its duration may help dictate post-pandemic planning. METHODS: Using assays to detect antibodies to either nucleocapsid (N) or spike (S) proteins performed on specimens from 39,086 individuals with confirmed positive COVID-19 by reverse transcription-polymerase chain reaction (RT-PCR) from March 2020 to January 2021, we analyzed nationwide seropositivity rates of IgG up to 300 days following patients' initial positive NAAT test. Linear regression identified trends in seropositivity rates and logistic regression tested positive predictability by age, sex, assay type and days post-infection. FINDINGS: Seropositivity of IgG antibodies to both SARS-CoV-2 S and N-proteins followed a linear trend reaching approximately 90% positivity at 21 days post-index. The rate of N-protein seropositivity declined at a sharper rate, decaying to 68·2% [95% CI: 63·1-70·8%] after 293 days, while S-antibody seropositivity maintained a rate of 87·8% [95% CI: 86·3-89·1%] through 300 days. In addition to antigen type and the number of days post-positive PCR, age and gender were also significant factors in seropositivity prediction, with those under 65 years of age showing a more sustained seropositivity rate. INTERPRETATION: Observational data from a national clinical laboratory, though limited by an epidemiological view of the U.S. population, offer an encouraging timeline for the development and sustainability of antibodies up to ten months from natural infection and could inform post-pandemic planning.

Comparison of PET imaging with 64Cu-liposomes and 18F-FDG in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch model of oral dysplasia and squamous cell carcinoma.

PURPOSE: Currently, 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG) is the gold standard radiotracer for staging of head and neck cancer; however, the low sensitivity of this tracer can impede detection of early lesions. (64)Cu-liposomes accumulate in various cancers and provide both a sensitive tracer and an indication of the biodistribution of nanotherapeutics. Here, the accumulation of (64)Cu-liposomes in early and established cancers is assessed and compared with (18)F-FDG in a head and neck cancer model. METHODS: Lesions ranging from mild dysplasia to squamous cell carcinoma were induced in a hamster model of head and neck cancer by topical application of 7,12-dimethylbenz[a]anthracene to the buccal pouch. The hamsters were imaged with micro-positron emission tomography using (18)F-FDG and (64)Cu-liposomes. RESULTS: At 24 h postinjection, (64)Cu-liposome accumulation exceeded the accumulation of (18)F-FDG in every pathologic grade. The lesion-to-cheek pouch (background) ratio and lesion-to-brain ratio were also higher for (64)Cu-liposomes than for (18)F-FDG. CONCLUSION: Imaging of a nanotracer such as (64)Cu-liposomes can improve the visualization of head and neck tumors. Accumulation of liposomal particles in head and neck tumors over various pathologic grades averaged 3.5%ID/cc demonstrating the potential for liposomal therapy with targeted chemotherapeutic agents.

Endoscopic fluorescence lifetime imaging for in vivo intraoperative diagnosis of oral carcinoma.

A clinically compatible fluorescence lifetime imaging microscopy (FLIM) system was developed. The system was applied to intraoperative in vivo imaging of head and neck squamous cell carcinoma (HNSCC). The endoscopic FLIM prototype integrates a gated (down to 0.2 ns) intensifier imaging system and a fiber-bundle endoscope (0.5-mm-diameter, 10,000 fibers with a gradient index lens objective 0.5 NA, 4-mm field of view), which provides intraoperative access to the surgical field. Tissue autofluorescence was induced by a pulsed laser (337 nm, 700 ps pulse width) and collected in the 460 ± 25 nm spectral band. FLIM experiments were conducted at 26 anatomic sites in ten patients during head and neck cancer surgery. HNSCC exhibited a weaker florescence intensity (~50% less) when compared with healthy tissue and a shorter average lifetime (τ(HNSCC) = 1.21 ± 0.04 ns) than the surrounding normal tissue (τN = 1.49 ± 0.06 ns). This work demonstrates the potential of FLIM for label-free head and neck tumor demarcation during intraoperative surgical procedures.

Time-resolved laser-induced fluorescence spectroscopy as a diagnostic instrument in head and neck carcinoma.

OBJECTIVE: The objectives of this study were to 1) determine differences in lifetime fluorescence between normal and malignant tissue of the upper aerodigestive tract, and 2) evaluate the potential of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as a diagnostic instrument for head and neck squamous cell carcinoma (HNSCC). STUDY DESIGN: Cross-sectional study. SETTING: University-based medical center. SUBJECTS AND METHODS: Nine patients with suspected HNSCC were included. In the operating room, a nitrogen pulse laser (337 nm, 700-picosecond pulse width) was used to induce tissue autofluorescence of normal tissue and suspected malignant lesions. Spectral intensities and time-domain measurements were obtained and compared with the histopathology at each site. A total of 53 sites were measured. The fluorescence parameters that provided the most discrimination were determined. RESULTS: Differences in spectral intensities allowed for discrimination between malignant and normal tissue. The spectral intensity of malignant tissue was lower than that of normal tissue, and a shift of peak intensity to a longer wavelength was observed in the normalized spectrum of malignant tissue in the range of 360 to approximately 660 nm. Multiple time-resolved fluorescence parameters provided the best diagnostic discrimination between normal tissue and carcinoma, including average lifetimes (i.e., at 390 nm: 1.7 +/- 0.06 ns [not significant] for normal and 1.3 +/- 0.06 ns for tumor, P = 0.0025) and the second-order Laguerre expansion coefficient (LEC-2) (i.e., at 460 nm: 0.135 +/- 0.001 for normal and 0.155 +/- 0.007 for tumor, P < 0.05). CONCLUSION: These findings highlight some of the differences in lifetime fluorescence between normal and malignant tissue. TR-LIFS has potential as a noninvasive diagnostic technique for HNSCC.

Pediatric lipoblastoma in the head and neck: a systematic review of 48 reported cases.

BACKGROUND: Lipoblastoma is an exceedingly rare cause of pediatric head and neck masses. There have been 47 cases previously reported in the English literature. We present an additional case and review of the available literature on this rare neoplasm. OBJECTIVE: To review and assess the current published literature regarding the efficacy of preserving neurovascular structures in the surgical management of pediatric lipoblastoma. METHODS: Literature analysis of case reports was performed. MEDLINE was searched for the terms "neonatal lipoblastoma", "lipoblastomatosis", and "benign lipoblastoma". Results in the English literature were mined for relevant clinical data when available. The citations of case reviews found were searched to find additional cases. RESULTS: Including our new case, a total of 48 cases of head and neck lipoblastoma have been reported in the English literature within 23 manuscripts. Four manuscripts presented cases series (Evidence Based Medicine Level 4) and 19 were case reports (Level 5). The median sample size was 1 (range 1-4). For those 14 articles (N=23 cases) reporting follow-up, the median follow-up duration was 22 months. Male to female ratio was 2.1:1 with an average age at presentation of 2.1 years (range: newborn to 12 years). Lesions ranged from 3 to 12 cm in longest diameter. Recurrence was seen in 27% of patients in which there was at least 1-year follow-up. The most common presenting symptoms were painless enlarging neck mass (53%, 17/32) and respiratory distress (12%, 4/32). An exact binomial sign test indicated that most authors recommend conservative complete excision with preservation of vital structures with 10 of 11 authors giving a stance supporting conservative surgical resection, p=.012. CONCLUSIONS: Our findings suggest that although total excision is ideal and curative, subtotal resection may be a viable treatment alternative for lipoblastoma of the head and neck. This tumor presents a clinical challenge and should be considered in infants presenting with a cervical mass. It is difficult to differentiate from the much more common lymphangioma on clinical and radiological examination. Additionally, the potential for rapid growth and adhesion to neurovascular tissue makes surgical resection arduous. Nonetheless, recurrence rates for head and neck lipoblastomas are similar to those rates observed elsewhere in the body.

Time-resolved fluorescence spectroscopy as a diagnostic technique of oral carcinoma: Validation in the hamster buccal pouch model.

OBJECTIVE: To investigate the benefit of using time-resolved, laser-induced fluorescence spectroscopy for diagnosing malignant and premalignant lesions of the oral cavity. DESIGN: The carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) was applied to 1 cheek pouch of 19 hamsters. The contralateral pouch and the cheek pouches of 3 hamsters without DMBA exposure served as controls. SETTING: University of California, Davis. PARTICIPANTS: Twenty-two golden/Syrian hamsters. INTERVENTION: A nitrogen pulse laser was used to induce tissue autofluorescence between the wavelengths of 360 and 650 nm. MAIN OUTCOME MEASURES: Spectral intensities and time-domain measurements were obtained and compared with the histopathologic findings at each corresponding site. RESULTS: Spectral intensities and lifetime values at 3 spectral bands (SBs; SB1 = 380 +/- 10 nm; SB2 = 460 +/- 10 nm, and SB3 = 635 +/- 10 nm) allowed for discrimination among healthy epithelium, dysplasia, carcinoma in situ, and invasive carcinoma. The lifetime values at SB2 were the most important when distinguishing the lesions using only time-resolved parameters. An algorithm combining spectral fluorescence parameters derived from both spectral and time-domain parameters (peak intensities, average fluorescence lifetimes, and the Laguerre coefficient [zero-order]) for healthy epithelium, dysplasia, carcinoma in situ, and invasive carcinoma provided the best diagnostic discrimination, with 100%, 100%, 69.2%, and 76.5% sensitivity and 100%, 92.2%, 97.1%, and 96.2% specificity, respectively. CONCLUSIONS: The addition of time-resolved fluorescence-derived parameters significantly improves the capability of fluorescence spectroscopy-based diagnostics in the hamster buccal pouch. This technique provides a potential noninvasive diagnostic instrument for head and neck cancer.

Fluorescence lifetime imaging microscopy: in vivo application to diagnosis of oral carcinoma.

A compact clinically compatible fluorescence lifetime imaging microscopy (FLIM) system was designed and built for intraoperative disease diagnosis and validated in vivo in a hamster oral carcinogenesis model. This apparatus allows for the remote image collection via a flexible imaging probe consisting of a gradient index objective lens and a fiber bundle. Tissue autofluorescence (337 nm excitation) was imaged using an intensified CCD with a gate width down to 0.2 ns. We demonstrate a significant contrast in fluorescence lifetime between tumor (1.77+/-0.26 ns) and normal (2.50+/-0.36 ns) tissues at 450 nm and an over 80% intensity decrease at 390 nm emission in tumor versus normal areas. The time-resolved images were minimally affected by tissue morphology, endogenous absorbers, and illumination. These results demonstrate the potential of FLIM as an intraoperative diagnostic technique.

Treatment with 1-alpha,25-dihydroxyvitamin D3 (vitamin D3) to inhibit carcinogenesis in the hamster buccal pouch model.

OBJECTIVE: To investigate whether systemic therapy with 1-alpha,25-dihydroxyvitamin D(3) (vitamin D(3) [hereinafter, VD(3)]) prevents tumor formation in a hamster buccal pouch model of carcinogenesis. DESIGN: Randomized trial in which a known carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA), was applied to the buccal pouch of 40 hamsters. Animals were randomized to receive systemic VD(3) or no treatment and killed at 2, 6, and 14 weeks after the initiation of DMBA exposure. SETTING: Academic medical center. SUBJECTS: Forty male golden Syrian hamsters, aged 5 to 6 weeks, were used. INTERVENTIONS: A dose of 0.25 mug/kg of VD(3) via intraperitoneal injection was given to 20 animals 3 times per week. Of the remaining 20 control animals, 5 received placebo vehicle injection, and 15 received no further treatment. MAIN OUTCOME MEASURES: Timing, size, and number of tumors that developed in the 2 groups. RESULTS: Only 1 hamster treated with VD(3) developed a confirmed neoplasm compared with 7 of the control animals (P < .01). The mean +/- SD total diameter of gross lesions per animal in the VD(3)-treated group was 1.2 +/- 1.9 mm compared with 6.8 +/- 6.6 mm in the control group (P = .03). The time to onset of lesion formation was significantly delayed in those animals treated with VD(3), with a mean +/- SD time to development of 13.4 +/- 0.9 weeks, while the control animals developed lesions at 11.2 +/- 1.7 weeks (P = .02). CONCLUSIONS: Systemic VD(3) therapy delays carcinogenesis in the hamster buccal pouch model. Further investigation into the mechanisms through which VD(3) inhibits carcinogenesis may lead to development of effective chemopreventive agents to combat head and neck cancer.