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Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples
Background: Congenital hypothyroidism (CH) is a significant health concern globally, with severe consequences if left untreated. Newborn screening (NBS) programs play a pivotal role in early detection and intervention of CH. However, due to resource constraints, South Africa lacks a national NBS pro...
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| Format: | Thesis |
| Language: | English English |
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Department of Pathology
2025
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| _version_ | 1867613316237492224 |
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| access_status_str | Open Access |
| author | Mahomed, Mariam |
| author2 | Rusch, Jody |
| author_browse | Mahomed, Mariam Rusch, Jody |
| author_facet | Rusch, Jody Mahomed, Mariam |
| author_sort | Mahomed, Mariam |
| collection | Thesis |
| description | Background: Congenital hypothyroidism (CH) is a significant health concern globally, with severe consequences if left untreated. Newborn screening (NBS) programs play a pivotal role in early detection and intervention of CH. However, due to resource constraints, South Africa lacks a national NBS program. This study aimed to establish reference intervals for thyroid stimulating hormone (TSH) and free thyroxine (FT4) in cord blood, as well as to compare the previous TSH radioimmunoassay with the current electrochemiluminescence immunoassay. Methods: Utilizing residual samples from the Peninsula Maternal and Neonatal Services (PMNS) CH Screening Program, this prospective study collected samples from uncomplicated pregnancies, resulting in 121 samples for reference interval analysis. Additionally, 14 samples within pathological ranges were selected, bringing the total for the method comparison study to 135. TSH and FT4 levels were determined by automated immunoassay on the Roche Cobas® 6000 analyser (Elecsys TSH and Elecsys FT4 III assays). The data analysis was performed following relevant CLSI guidelines (CLSI EP28-A3c and CLSI EP09-A3). Results: In the reference interval study, the mean birth weight was 3,211g (+/-387g). Non-parametric methodology yielded a TSH reference interval of 1.85 to 15.35 mIU/L and a free T4 reference interval of 13.0 to 20.4 pmol/L. The TSH method comparison study demonstrated strong agreement between the radioimmunoassay and electrochemiluminescence immunoassay (R-squared=0.98; Lin's CCC=0.97). Bland-Altman analysis revealed most points within the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) total allowable error goals for TSH, with RIA results showing a small positive bias. Conclusion: This study establishes reference intervals for cord blood TSH and FT4 in a South African context. Cord blood presents advantages for CH screening in resource-constrained settings, integrating with existing labour and delivery protocols while minimizing logistical challenges. The established intervals align with existing literature and methodologies, supporting their validity and applicability. Continued monitoring of the CH program and clinical outcomes is crucial for validating the study results in a clinical context, ensuring ongoing relevance and accuracy. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/41737 |
| institution | University of Cape Town (South Africa) |
| language | English eng |
| last_indexed | 2026-06-10T12:34:10.861Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Department of Pathology |
| publisherStr | Department of Pathology |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/41737 Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples Mahomed, Mariam Rusch, Jody Vreede, Helena Hormone Blood samples Background: Congenital hypothyroidism (CH) is a significant health concern globally, with severe consequences if left untreated. Newborn screening (NBS) programs play a pivotal role in early detection and intervention of CH. However, due to resource constraints, South Africa lacks a national NBS program. This study aimed to establish reference intervals for thyroid stimulating hormone (TSH) and free thyroxine (FT4) in cord blood, as well as to compare the previous TSH radioimmunoassay with the current electrochemiluminescence immunoassay. Methods: Utilizing residual samples from the Peninsula Maternal and Neonatal Services (PMNS) CH Screening Program, this prospective study collected samples from uncomplicated pregnancies, resulting in 121 samples for reference interval analysis. Additionally, 14 samples within pathological ranges were selected, bringing the total for the method comparison study to 135. TSH and FT4 levels were determined by automated immunoassay on the Roche Cobas® 6000 analyser (Elecsys TSH and Elecsys FT4 III assays). The data analysis was performed following relevant CLSI guidelines (CLSI EP28-A3c and CLSI EP09-A3). Results: In the reference interval study, the mean birth weight was 3,211g (+/-387g). Non-parametric methodology yielded a TSH reference interval of 1.85 to 15.35 mIU/L and a free T4 reference interval of 13.0 to 20.4 pmol/L. The TSH method comparison study demonstrated strong agreement between the radioimmunoassay and electrochemiluminescence immunoassay (R-squared=0.98; Lin's CCC=0.97). Bland-Altman analysis revealed most points within the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) total allowable error goals for TSH, with RIA results showing a small positive bias. Conclusion: This study establishes reference intervals for cord blood TSH and FT4 in a South African context. Cord blood presents advantages for CH screening in resource-constrained settings, integrating with existing labour and delivery protocols while minimizing logistical challenges. The established intervals align with existing literature and methodologies, supporting their validity and applicability. Continued monitoring of the CH program and clinical outcomes is crucial for validating the study results in a clinical context, ensuring ongoing relevance and accuracy. 2025-09-10T07:02:20Z 2025-09-10T07:02:20Z 2025 2025-09-10T06:59:41Z Thesis / Dissertation Masters MMed http://hdl.handle.net/11427/41737 en eng application/pdf Department of Pathology Faculty of Health Sciences University of Cape Town |
| spellingShingle | Hormone Blood samples Mahomed, Mariam Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples |
| thesis_degree_str | Master's |
| title | Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples |
| title_full | Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples |
| title_fullStr | Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples |
| title_full_unstemmed | Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples |
| title_short | Determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples |
| title_sort | determination of reference intervals and decision limits for thyroid stimulating hormone and thyroxine on cord blood samples |
| topic | Hormone Blood samples |
| url | http://hdl.handle.net/11427/41737 |
| work_keys_str_mv | AT mahomedmariam determinationofreferenceintervalsanddecisionlimitsforthyroidstimulatinghormoneandthyroxineoncordbloodsamples |