Presence Of False-negative Results Research Articles

PSXII-21 Pregnancy associated glycoproteins for pregnancy diagnosis on day 25 of gestation

Abstract The objective of this study was to evaluate the use of plasma concentrations of pregnancy associated glycoproteins (PAG) for pregnancy diagnosis in beef cows on day 25 of gestation. Additionally, differences in circulating concentrations of PAG among cows that experienced late embryonic/early fetal mortality (LEM) were evaluated. Beef cows (n = 214) were exposed to the 7-d CO-Synch + CIDR protocol followed by fixed-time artificial insemination (day 0). Blood samples were collected on days 25 and 29 to determine circulating concentrations of PAG and ultrasonography on day 29 was used as the gold-standard method for pregnancy diagnosis. On days 25 and 29, PAG concentrations were greater (P < 0.001) in pregnant compared with non-pregnant cows. Sensitivity, specificity, positive predicted value (PPV), negative predicted value (NPV), and accuracy on day 25 were 87, 80, 83, 84, and 83%, respectively. Sensitivity, specificity, PPV, NPV, and accuracy for PAG on day 29 were 99, 94, 96, 97, and 99%, respectively. Pairwise comparison of receiver operating characteristics curve analysis indicated greater area under the curve for PAG on day 29 compared with day 25 (P < 0.001). There were no differences in plasma concentrations of PAG on day 25 among cows that experienced LEM compared to cows that maintained pregnancy (P = 0.46). Concentrations of PAG on day 29 were reduced (P = 0.03) in cows that experienced LEM compared with cows that maintained pregnancy, and were not different between LEM and non-pregnant cows (P = 0.12). In summary, cows that experienced LEM had decreased plasma concentrations of PAG compared with cows that maintained pregnancy. The PAG assay utilized in this study yielded accurate pregnancy diagnosis results on day 29 of gestation: however, the presence of false negative results (NPV = 84%) limits its use on day 25 of gestation.

One-Year Update on Salivary Diagnostic of COVID-19.

Background: Coronavirus disease 2019 (COVID-19) is a global health problem, which is challenging healthcare worldwide. In this critical review, we discussed the advantages and limitations in the implementation of salivary diagnostic platforms of COVID-19. The diagnostic test of COVID-19 by invasive nasopharyngeal collection is uncomfortable for patients and requires specialized training of healthcare professionals in order to obtain an appropriate collection of samples. Additionally, these professionals are in close contact with infected patients or suspected cases of COVID-19, leading to an increased contamination risk for frontline healthcare workers. Although there is a colossal demand for novel diagnostic platforms with non-invasive and self-collection samples of COVID-19, the implementation of the salivary platforms has not been implemented for extensive scale testing. Up to date, several cross-section and clinical trial studies published in the last 12 months support the potential of detecting SARS-CoV-2 RNA in saliva as a biomarker for COVID-19, providing a self-collection, non-invasive, safe, and comfortable procedure. Therefore, the salivary diagnosis is suitable to protect healthcare professionals and other frontline workers and may encourage patients to get tested due to its advantages over the current invasive methods. The detection of SARS-CoV-2 in saliva was substantial also in patients with a negative nasopharyngeal swab, indicating the presence of false negative results. Furthermore, we expect that salivary diagnostic devices for COVID-19 will continue to be used with austerity without excluding traditional gold standard specimens to detect SARS-CoV-2.

Real-time reverse-transcription PCR in the diagnosis of influenza A (H1N1)v in intensive care unit adult patients

Regarding the interesting article on novel influenza A (H1N1)v infection in intensive care adult patients with severe respiratory failure recently published in Critical Care [1], we should like to make the following comments. The authors found that real-time RT-PCR for novel influenza A (H1N1)v virus in nasopharyngeal swabs on intensive care unit (ICU) admission was negative in four patients (12.5%) who later had a positive PCR result in respiratory secretions obtained at intubation, and concluded that 'a negative PCR result at admission should not exclude influenza A (H1N1)v due to the presence of false negative results in at least 10% cases' [1]. We of course understand what the authors meant. In our opinion, however, this assumption is formally inaccurate, and is somewhat misleading, as it might be inferred that real-time RT-PCR gives at least 10% of false negative results in patients with overt symptomatic influenza requiring ICU admission. The negative results reported by the authors cannot be considered true false negative RT-PCR results, as samples were not tested in parallel by a different assay yielding a positive result - in fact, RT-PCR, which was used at participating centers, is currently the standard method for the diagnosis of influenza. Optimal sensitivity of RT-PCR and rapid antigen tests is achieved when upper tract respiratory specimens are collected within the first few days after the onset of symptoms, as appeared to be the case for the above-mentioned patients. Inappropriate sampling or specimen processing or suboptimal sensitivity of the PCR assay used most probably accounted for the negative results. No speculation on this matter can be made because the microbiological information given to the readers was rather scarce. The possibility of false negative RT-PCR results for influenza A (H1N1)v in severely ill patients requiring admission to ICUs is a very important issue that must be further investigated.