Browsing by Subject "sensitivity"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Open Access
    DEGREE OF POLARIZATION AND SOURCE COUNTS OF FAINT RADIO SOURCES FROM STACKING POLARIZED INTENSITY
    (2014) Stil, J M; Keller, B W; George, S J; Taylor, A R
    We present stacking polarized intensity as a means to study the polarization of sources that are too faint to be detected individually in surveys of polarized radio sources. Stacking offers not only high sensitivity to the median signal of a class of radio sources, but also avoids a detection threshold in polarized intensity, and therefore an arbitrary exclusion of source with a low percentage of polarization. Correction for polarization bias is done through a Monte Carlo analysis and tested on a simulated survey. We show that the non-linear relation between the real polarized signal and the detected signal requires knowledge of the shape of the distribution of fractional polarization, which we constrain using the ratio of the upper quartile to the lower quartile of the distribution of stacked polarized intensities. Stacking polarized intensity for NVSS sources down to the detection limit in Stokes I, we find a gradual increase in median fractional polarization that is consistent with a trend that was noticed before for bright NVSS sources, but is much more gradual than found by previous deep surveys of radio polarization. Consequently, the polarized radio source counts derived from our stacking experiment predict fewer polarized radio sources for future surveys with the Square Kilometre Array and its pathfinders.
  • Thumbnail Image
    Item
    Open Access
    Ototoxicity Monitoring using Automated Extended High-Frequency Audiometry and the Sensitive Range of Ototoxicity in Patients with MDR-TB
    (2020) Greeff, Wildine Marion; Petersen, Lucretia; Hlayisi, Vera-Genevey
    Background: Disabling hearing loss is a global burden. This burden is worsened by the emergence of multi-drug resistant tuberculosis (MDR-TB). Some of the medications used to treat MDR-TB are damaging to the cochlea and auditory nerve (ototoxic) and can lead to permanent hearing loss and/or balance disorders. Ototoxicity monitoring aims to reduce this burden by preventing or minimising the damage caused by ototoxic treatment as it can progress and worsen speech perception difficulties. However, the proposed test battery for ototoxicity monitoring is lengthy and demands active participation which is not ideal for ill patients (such as those on MDR-TB treatment). The Sensitive Range of Ototoxicity (SRO) technique is recommended to shorten the test time. The SRO consists of seven consecutive relatively high frequencies determined from the highest frequency the participant responded to. The SRO technique is time efficient. Although the SRO technique provides the prospect of a shortened test battery, there is still a global lack of audiologists. Automated audiometry is a vital application for testing especially when audiologists are not available to physically do the test. Automated audiometry has been previously validated. Clinically, automated audiometry is objective and allows for standardisation. Even though automated audiometry helps improve access to monitoring more patients, patient preference is an important factor when using automated audiometry to ensure patient-centred care is not compromised. Aims and Objectives: This study aimed to investigate the specificity and sensitivity of the SRO technique with automated audiometry compared to the gold standard (manual audiometry). This comparison was made by firstly, determining the testing time efficiency and the correlation of thresholds obtained with the different test methods and, secondly, testing the diagnostic value of automated audiometry using the SRO technique. The incidence of an ototoxicity-induced hearing loss was described by determining the time interval between starting ototoxic MDR-TB treatment and the onset of a significant threshold shift (STS) according to ASHA's criteria. Lastly, the test method preference of the participants with MDR-TB was described and compared using a short exit survey. Study Design: A prospective repeated-measures study design was used. Participants were chosen based on a risk factor (i.e. exposure to ototoxic medication) for an outcome of interest (i.e. the presence or absence of an STS). With a repeated measures study, multiple tests using different test methods can be compared with the same sample. Participants: Twenty-seven in-patients at Brooklyn Chest Hospital and DP Marais TB Hospital with normal hearing and on MDR-TB medication were included in the study. Their age range was from 19 to 51 years old with an average age of 33 years old. Non-probability convenience sampling was used as it was cost-effective, reduced data collection time and was relatively easy to execute. Data collection materials and procedures: The procedure for data collection included weekly follow-up testing for a maximum of four weeks. The test battery was as follows: an auditory symptom questionnaire, otoscopy examination, and manual and automated audiometry using the SRO technique with a fifteen-minute break in between. Participants were tested with the KUDUwave ™ in a non-sound treated room. The frequency range was determined with the SRO technique. If an STS was obtained, the patient was discharged from the study after completing an exit survey. Statistics: Analysis included descriptive statistics and inferential statistics. A Bonferroni corrected p-value (initially p ≤ 0.05) was used. Manual and automated audiometry thresholds were compared using the Pearson's Correlation Coefficient test. Manual and automated audiometry testing time and threshold means were compared using paired sample's t-tests. The diagnostic value of automated audiometry with the SRO technique was assessed with Receiver Operating Characteristics (ROC) Curves. Results: Manual audiometry was statistically more time-efficient compared to automated audiometry by an average of one minute and ten seconds (t (94) = -5.44; p< 0.003). There was a strong positive correlation for both left and right ears between the thresholds' obtained from manual and automated audiometry at 8kHz to 16 kHz (df> 28 = r > 0.70, p< 0.003). Automated audiometry was found to be a fair diagnostic test (area under the curve was 0.75; p= 0.002). Also, the ROC curve revealed that automated audiometry had a sensitivity of 61% and specificity of 90% when compared to manual audiometry (gold standard). Only participants that started data collection within 31 days after starting their MDR-TB treatment were included in the analysis of determining the incidence of an ototoxicity-induced hearing loss (n= 24 ears). This study found that 41.67% of ears (n= 10) had an ototoxicity-induced hearing loss. A box and whisker plot revealed that data was skewed to the right (i.e. more variation in data between the median and the maximum values) and that the median number of days for an ototoxicity-induced hearing loss to appear was 33 days. Secondly, 55.55% of participants (n=15 out of 27) reported auditory symptoms before data collection commencement. Aural fullness was the most reported symptom (n= eight out of 15). Ten out of 15 (66.66%) participants that reported auditory symptoms obtained an ototoxicity-induced hearing loss. Lastly, most participants (i.e. 13 out of 19; 68.42%) that completed the exit survey had no preference between manual or automated audiometry. The common rationale among these participants was “No difference noted.” Conclusion: This research study has revealed that manual audiometry was more time-efficient compared to automated audiometry in patients with MDR-TB. Also, automated audiometry was a fair diagnostic test. It may aid in reducing the disproportionate audiologist to patient ratio, especially in a developing country. However, manual audiometry (with the SRO technique) is more clinically appropriate in patients that are difficult-to-test. Secondly, audiometric settings can be changed to accommodate testing frequencies in 1/6 octaves so that the SRO technique can be clinically adopted. An ototoxicity-induced hearing loss seems to appear 33 days after ototoxic MDR-TB treatment commencement. Aural fullness was a commonly reported symptom among participants with MDRTB. Aural fullness is omnipresent in peripheral auditory pathologies. Therefore, auditory symptoms reported by patients' needs a comprehensive audiological investigation. Lastly, more research is needed on how patients (and clinicians) experience the advances in technology innovation especially in audiology where technology innovation is continuously evolving.
  • Thumbnail Image
    Item
    Open Access
    Search for magnetic monopoles and stable particles with high electric charges in 8 TeV pp collisions with the ATLAS detector
    (2016) Aad, G; Abbott, B; Abdallah, J; Abdinov, O; Aben, R; Abolins, M; AbouZeid, O S; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, B S; Adamczyk, L; Adams, D L; Adelman, J; Adomeit, S; Adye, T; Affolder, A A; Agatonovic-Jovin, T; Agricola, J; Aguilar-Saavedra, J A; Ahlen, S P; Ahmadov, F; Aielli, G; Akerstedt, H; Åkesson, T P A; Akimov, A V; Alberghi, G L; Albert, J; Albrand, S; Alconada Verzini, M J; Aleksa, M
    A search for highly ionizing particles produced in proton-proton collisions at 8 TeV center-of-mass energy is performed by the ATLAS Collaboration at the CERN Large Hadron Collider. The data set us ...
  • No Thumbnail Available
    Item
    Open Access
    Social vulnerability of fishing communities in the southern Cape to change, including additional pressures of COVID-19
    (2025) Netshithuthuni, Humbelani; Gammage, Louise; Ward, Catherine
    Marine systems are critical for providing support to the lives and livelihood of millions of people including small-scale fishers (SSFs). However, these communities are faced with many challenges such as resource scarcity, climate change and variability, policy and regulation and the more recent COVID-19 pandemic. This dissertation examines the social vulnerabilities of SSFs in the southern Cape, particularly in the two fishing towns of Bitouville and Melkhoutfontein, to better understand how challenges impact the ability of SSFs to support their livelihoods and how this has changed over the last 10 years. This research made use of a mixed-method technique that included both qualitative and quantitative aspects, drawing on the Global Understanding and Learning for Local Solutions (GULLS) survey that was first implemented in 2013/14 and amended to suit the local context of the southern Cape, which was administered through face-to-face interviews in 2023. Social vulnerability scores were calculated in line with the GULLS framework to gain a deeper insight into the vulnerabilities faced by SSFs and how these have evolved over the last decade. In both Bitouville and Melkhoutfontein communities, vulnerabilities of SSFs were exacerbated by the more recent COVID-19 pandemic, which led to the loss of income sources and available sea days, which in turn contributed to food insecurity. Regarding the evolution of the drivers of changes in 2013/14 and 2023, the results of this study revealed an increase in the social vulnerability scores in both Bitouville and Melkhoutfontein over time as a result of increased exposure to challenges linked to resource scarcity, climate change and variability, and policy and regulation. For example, the continued delay in the implementation of South Africa's small-scale fishing policy (SSFP) has contributed to increased vulnerability as this impacts SFFs' access to fishing rights. The results also revealed that SSFs in Bitouville faced more vulnerabilities compared to their counterparts in Melkhoutfontein, which was attributed to their higher social dependency on fishing, limited livelihood opportunities, higher exposure to environmental changes, and lower adaptive capacity. The vulnerability of these two fishing communities is thus increasing due to compounding stressors such as resource scarcity, climate variability, the COVID-19 pandemic and policy and regulation. This research highlighted the importance of improving the adaptive strategies of SSFs, as limited improvement in these strategies places the livelihoods of these fishing communities at greater risk and exacerbates vulnerabilities in the important, livelihood-intensive southern Cape fisheries.
  • No Thumbnail Available
    Item
    Open Access
    The performance of respiratory illness surveillance case definitions to detect Bordetella pertussis in children aged < 5 years seeking healthcare for respiratory illness in South Africa, 2017-2023
    (2025) Jensen, Katherine; De Voux, Alex; Walaza, Sibongile
    Background: Pertussis is vaccine‐preventable and requires surveillance to guide interventions. Assessing the performance of syndromic surveillance and the World Health Organization (WHO) pertussis case definitions can improve sensitivity and accuracy in detecting laboratory‐confirmed Bordetella pertussis, ensuring effective monitoring in South Africa. Methods: We conducted a secondary analysis of respiratory illness surveillance data among children aged <5 years across sentinel sites from January 2017 through December 2023. Participants were enrolled as either outpatients eligible for influenza‐like illness (ILI), or hospitalised patients eligible for severe respiratory infection (SRI) surveillance. Nasopharyngeal swabs were tested for B. pertussis using polymerase chain reaction (PCR). Sensitivity, specificity, and other performance indicators of case definitions were evaluated against PCR results. Results: Of 23,887 participants, 23,640 (99.0%) had PCR results. B. pertussis was detected in 0.7% (30/4,125) from ILI and 1.6% (314/19,517) from SRI surveillance. Compared to the WHO pertussis case definition, a modified WHO pertussis case definition which includes apnoea and omits cough duration, improved sensitivity (ILI: 30.0% vs. 43.3%; SRI: 55.7% vs. 60.2%), but reduced specificity (ILI: 90.5% vs. 75.8%; SRI: 88.3% vs. 80.9% %). Negative predictive values were high for both definitions (ILI: 99.5% vs. 99.4%; SRI: 99.2% vs. 99.2%). The WHO pertussis case definition missed 44.3% of hospital laboratory‐confirmed cases, while the modified case definition missed 39.8%. Conclusion: Both WHO and modified pertussis case definitions missed many laboratory‐confirmed pertussis cases, likely underestimating disease burden. Revising the WHO pertussis case definition and integrating pertussis into syndromic surveillance is recommended to improve detection while optimising resources.