Electronic Theses and Dissertations (Masters)
Permanent URI for this collectionhttps://hdl.handle.net/10539/38221
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Item Comparison of second and third generation parathyroid hormone (PTH) assays performed at Charlotte Maxeke Johannesburg Academic Hospital – Are they fit for purpose?(University of the Witwatersrand, Johannesburg, 2023-11) Nhlapo, Nokuthula; Jacob, Doreen; Maphayi, MphoBackground: Parathyroid hormone (PTH) measurement is crucial in the investigation of calcium and phosphate disorders and in the management of chronic kidney disease (CKD). Available PTH assays include second (intact PTH) and third generation (PTH 1-84) assays. Intact PTH assays are widely available and used for clinical guidelines but overestimate PTH in CKD. PTH 1-84 assays are more specific, but lack of standardisation has complicated clinical interpretation. The study aimed to compare the second and third generation assays to determine the difference in analytical performance and the effect on clinical interpretation. Methods: A method comparison was done on 481 patient samples with PTH requested at Charlotte Maxeke Johannesburg Academic Hospital. PTH was measured in each sample using both intact PTH and PTH 1-84 assays. Passing Bablok regression and Bland Altman plots were performed to determine method agreement and bias. Analytical performance was assessed using the European Federation of Clinical Chemistry and Laboratory Medicine biological variation specifications. Clinical performance was compared in the diagnosis of hypo- and hyperparathyroidism, and in predialysis and dialysis CKD based on current Kidney Disease Improving Global Outcomes guidelines. Results: Intact PTH had a higher median concentration than PTH 1-84 (9.93 vs 8.60 pmol/L, p<0.0001) but showed good correlation (r = 0.994 and p<0.0001). Regression analysis revealed significant systematic and proportional differences, with increased deviations at higher concentrations. The average bias was above allowable bias of 7.1%. Clinical interpretation of hypo- and hyperparathyroidism and predialysis and dialysis groups was unchanged. Conclusions: There was significant bias observed between the two PTH assays thus, they should not be used interchangeably. However, no significant changes in clinical interpretation were found when one assay was used over the other. The decision to use third over second generation PTH assay should consider the impact on clinical interpretation in the population.Item Epidemiology of laboratory-confirmed SARS-CoV-2 hospitalized cases in a tertiary hospital, Gauteng Province, South Africa, 1 April 2020 to 31 March 2021(University of the Witwatersrand, Johannesburg, 2021-12) Sikhosana, Mpho Lerato; Makatini, ZinhleGauteng Province (GP) was the most affected province in South Africa during the first year of the COVID-19 pandemic. We aimed to describe the epidemiology of COVID-19 cases admitted in one of the largest quaternary hospitals in the province during the two pandemic waves. We used data from the national hospital surveillance system, DATCOV, that recorded COVID-19 admissions at Charlotte Maxeke Johannesburg Academic Hospital in (GP) from 5 March 2020 to 27 March 2021. We used multivariable logistic regression to determine a) factors associated with hospitalization in the second compared to the first pandemic wave, and b) factors associated with in-hospital mortality. There were 1861 cases admitted during the study period. The mean age of the cases was 50 (IQR 37-61), 51.80% were females, and 58.68% were black. Of the total number of admissions, 2.10% were healthcare worker, 53.85% of whom were nurses. On admission, 91.99% of cases were admitted at a general ward while 5.86% were admitted at an intensive care unit. Overall, 10.59% of the cases required intensive care during their hospital stay. The case fatality ratio was the highest (28.54%) during wave 2 and lowest during pre-wave (11.49%). Compared to the first wave, factors associated with hospitalization during the second wave included age >80 years (adjusted odds ratio [aOR] 3.43, 95% CI 1.07-10.98) compared to ages 0-19 years, as well as being of other race (aOR 5.63, 95%CI 1.84-17.20) compared with White race. Regarding in-hospital mortality, associated factors included age groups 60-79 (aOR 4.53, 95%CI 1.03-19.86) and >80 (aOR 9.63, 95%CI 1.93-48.01) compared to ages 0-19 years; male sex (aOR 1.55, 95%CI 1.16-2.08); presence of an underlying comorbidity (aOR 1.99, 95%CI 1.45-2.71) 106 as well as being admitted during the second wave (aOR 1.54, 95%CI 1.12-2.10). Our study found that there was a higher risk of mortality during the second compared to the first wave, and other factors associated with mortality included older age, being male as well as having an existing comorbidity. These findings will help inform prevention strategies required to prevent high mortality rates during future waves of infection.Item Comparison of measured LDL cholesterol with calculated LDL-cholesterol using the Friedewald and Martin-Hopkins formulae in diabetic adults at Charlotte Maxeke Johannesburg Academic Hospital/NHLS Laboratory(University of the Witwatersrand, Johannesburg, 2023-01) Dintshi, Mogomotsi Portia; Kone, Ngalulawa; Khoza, SiyabongaBackground: National Cholesterol Education Programme Adult Treatment Panel III (NCEP ATP III) and the European Society of Cardiology recommends using low-density lipoprotein cholesterol (LDL-C) as a treatment target for cholesterol lowering therapy. The Friedewald formula underestimate LDL-C in non-fasted and hypertriglyceridemia patients. This study aimed to compare measured LDL-C to calculated LDL-C in diabetic patients using the Friedewald and Martin-Hopkins formulae. Methods: The data of 1 247 adult diabetes patients were retrospectively evaluated, and included triglycerides (TG), LDL-C, total cholesterol, and high-density lipoprotein cholesterol that were measured on the Roche Cobas® c702. Passing-Bablok regression analysis was used to determine the degree of agreement between measured LDL-C and calculated LDL-C using both formulae. The Bland-Altman plots were used to assess the bias at medical decision limits based on the 2021 European Society of Cardiology (ESC) guidelines on cardiovascular disease prevention in clinical practice. Results: Both formulae showed a good linear relationship against measured LDL-C. However, the Martin-Hopkins formula outperformed the Friedewald formula at LDL-C treatment target <1.4mmol/L. The Friedewald formula and the Martin-Hopkins formula had 14.9% and 10.9% mean positive bias, respectively. At TG-C ≥1.7 mmol/L, the Martin-Hopkins formula had a lower mean positive bias of 4.2 % (95 % CI 3.0-5.5) compared to the Friedewald formula, which had a mean positive bias of 21.8 % (95 % CI 19.9-23), which was higher than the NCEP ATP III recommended total allowable limit of 12%. Conclusion: The Martin-Hopkins formula performed better than the Friedewald formula at LDL-C of 1.4 mmol/L and showed the least positive bias in patients with hypertriglyceridemia.Item Validation of Roche immunoassay for severe acute respiratory virus 2/SARS-COV-2 in South Africa(University of the Witwatersrand, Johannesburg, 2023-01) Grove, Jurette Simone; George, Jaya; Mayne, ElizabethBackground: Serology testing is an important ancillary diagnostic to the reverse transcriptase polymerase chain reaction (RT-PCR) test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We aimed to evaluate the performance of the Roche Elecsys™ chemiluminescent immunoassay (Rotkreuz, Switzerland), that detects antibodies against the SARS-CoV-2 nucleocapsid antigen, at an academic laboratory in South Africa. Methods: Serum samples were collected from 312 donors with confirmed positive SARS CoV-2 RT-PCR tests, with approval from a large university’s human research ethics committee. Negative controls included samples stored prior to December 2019 and from patients who tested negative for SARS-CoV-2 on RT-PCR and were confirmed negative using multiple serology methods (n = 124). Samples were stored at –80 °C and analysed on a Roche cobas™ 602 autoanalyser. Results: Compared with RT-PCR, our evaluation revealed a specificity of 100% and overall sensitivity of 65.1%. The sensitivity in individuals > 14 days’ post-diagnosis was 72.6%, with the highest sensitivity 31–50 days’ post-diagnosis at 88.6%. Results were also compared with in-house serology tests that showed high agreement in majority of categories. Conclusions: The sensitivity at all-time points post-diagnosis was lower than reported in other studies, but sensitivity in appropriate cohorts approached 90% with a high specificity. The lower sensitivity at earlier time points or in individuals without symptomatology may indicate failure to produce antibodies, which was further supported by the comparison against in-house serology tests.Item The stability of C-peptide and insulin in plasma and serum samples under different storage conditions(University of the Witwatersrand, Johannesburg, 2023-10) Nkuna, Delhia Xikombiso; Maphayi, MphoObjectives: C-peptide and insulin are peptide hormones and their stability is affected by a number of pre-analytical factors. The study aimed to investigate the impact of sample type, storage temperature and time delays before centri-fugation and analysis on the stability of C-peptide and insulin. Methods: Ten healthy non-diabetic adults in fasting and non-fasting state were enrolled. 40 mL of blood was collected from each participant into SST and dipotassium EDTA tubes. Samples were centrifuged immediately or at timed intervals (8, 12, 48 and 72 h). After baseline measurements on the Roche Cobas e602 analyzer using electrochemiluminescence immunoassays, aliquots were stored at room temperature (RT), 2–8 and −20 °C for 4 h to 30 days. The percentage deviation (PD) from baseline was calculated and a change greater than desirable biological variation total error was considered clinically significant. Results: C-peptide was more stable in separated serum than plasma (PD of −5 vs. −13 %) samples stored at 2–8 °C for 7 days and was most unstable at RT when centrifugation was delayed (PD −46 % in plasma and −74 % in serum after 48 h). Insulin was more stable in plasma than in serum under the different storage conditions with a minimum PD of −1% when stored at −20 °C for 30 days. When samples were kept unspun at RT for 72 h, PD was −23 and −80 % in plasma and serum, respectively. Conclusions: C-peptide was more stable in serum provided the sample was centrifuged immediately and stored in the fridge or freezer while insulin was found to be more stable in EDTA plasma.