Browsing by Author "Silva, P."

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Characterising the Mould Rectification Process for Designing Scoliosis Braces: Towards Automated Digital Design of 3D-Printed Braces
(MDPI AG, 2021) Sanz-Pena, I.; Arachchi, S.; Halwala-Vithanage, D.; Mallikarachchi, S.; Kirumbara-Liyanage, J.; McGregor, A.; Silva, P.
The plaster-casting method to create a scoliosis brace consists of mould generation and rectification to obtain the desired orthosis geometry. Alternative methods entail the use of 3D scanning and CAD/CAM. However, both manual and digital design entirely rely on the orthotist expertise. Characterisation of the rectification process is needed to ensure that digital designs are as efficient as plaster-cast designs. Three-dimensional scans of five patients, pre-, and post-rectification plaster moulds were obtained using a Structure Mark II scanner. Anatomical landmark positions, transverse section centroids, and 3D surface deviation analyses were performed to characterise the rectification process. The rectification process was characterised using two parameters. First, trends in the external contours of the rectified moulds were found, resulting in lateral tilt angles of 81 ± 3.8° and 83.3 ± 2.6° on the convex and concave side, respectively. Second, a rectification ratio at the iliac crest (0.23 ± 0.04 and 0.11 ± 0.02 on the convex and concave side, respectively) was devised, based on the pelvis width to estimate the volume to be removed. This study demonstrates that steps of the manual rectification process can be characterised. Results from this study can be fed into software to perform automatic digital rectification.
Comparative Analysis of Albumin Measurement by Bromocresol Green Versus Capillary Zone Electrophoresis
(College of Chemical Pathologists of Sri Lanka, 2024) Harshanee, T.; Jayasekara, D.; Fernando, K.; Kulasinghe, M.; Silva, P.; Bandara, S.; Dayanath, B.K.P.T.
INTRODUCTION Quantitative assessment of albumin and globulins in serum protein electrophoresis (SPE) relies on the calculation derived from total protein measurements obtained from the biuret assay. Validation of these results involves comparing sample albumin concentration assessed using the bromocresol green (BCG) method to those obtained from capillary zone electrophoresis (CZE). This study aimed to assess the relationship between albumin values derived from SPE and routine spectrophotometric analysis with BCG method, and to establish a cut-off value to identify significant differences between the two values in SPE validation process. METHODS 187 serum samples were subjected to total protein assessment by biuret method, albumin assessment by BCG method, and SPE by CZE method. SPE derived albumin level using total protein values and BCG method indicated albumin values were analyzed by correlation analysis. The standard error for the difference (SEdif) between the two albumin results were calculated, with statistical significance set at p <0.05. Internal and external quality assessments were deemed acceptable for all three analytical procedures. RESULTS Mean albumin levels obtained via BCG and CZE methods were 38.3 mg/dL and 33.2 mg/dL, respectively, indicating a negative bias for the latter method. A strong correlation (r=0.844, p<0.001) was observed between albumin levels measured by BCG and CZE methods, with Bland-Altman analysis revealing an average negative bias of 5 mg/dL. Using SEdif at 95% significance, the maximum acceptable difference between the two albumin values was determined to be -5.4 mg/dL. CONCLUSIONS BCG method yielded higher albumin results compared to CZE method. This positive bias could be attributed to potential lack of specificity of BCG assay for albumin. A maximum allowable difference of 5.5 mg/dL between the two methods is suggested. Exceeding this threshold indicates potential issues with either the BCG albumin assay, biuret total protein assay, or SPE assay, necessitating further investigation for assay reliability, particularly in reporting SPE by CZE.
Comparative analysis of alkaline phosphatase with two assays using different buffers; diethanolamine (dea) and 2-amino-2-methyl-1-propanol (amp): establishing correlation factors for diagnostic consistency
(College of Chemical Pathologists of Sri Lanka, 2024) Jayasekara, D.; Fernando, K.; Kulasinghe, M.; Silva, P.; Madurangi, D.W.D.D.; De Silva, D.D.S.; Harshanee, K.G.A.T.; Bandara, S.R.R.; Dayanath, B.K.T.P.
INTRODUCTION AND OBJECTIVES Alkaline phosphatase (ALP) serves as a pivotal biomarker for bone and liver diseases, employing assays utilizing either 2-amino-2-methyl-1-propanol (AMP) (IFCC recommended) or diethanolamine (DEA) buffers, with the latter consistently yielding higher values. This study aimed to develop a correlation factor for ALP reagents using DEA buffer from supplier X, in comparison to routine automated ALP assay at the central laboratory using AMP.METHODS Twenty-five serum samples were analyzed in the central laboratory assay using AMP buffer in a fully automated analyzer with dedicated reagents and the test assay using DEA buffer on a semi-automated biochemistry analyzer within two hours of receipt. Both assays employed the same biochemical reaction, differing only in buffer composition. The linearity ranges for the test assay with DEA buffer and the routine assay with AMP buffer were determined as 1600 U/L and 800 U/L, respectively. RESULTS Patient samples exhibited ALP levels ranging from 0 to 339 U/L by routine assay. The correlation graph demonstrated a satisfactory R2>0.75, indicating adequate number of sample inclusion and quality. A correction factor of 1.2 was calculated for the ALP assay utilizing DEA, compared to the AMP-based assay, employing simple linear regression analysis.CONCLUSIONS According to the sample availability, only ALP levels up to 339 U/L by AMP-based assay were included. Therefore, the correction factor of 1.2 is applicable only up to an ALP level of 400 U/L with the DEA-based assay, necessitating dilution of samples with higher values for the correlation factor’s application. This study indicates a correction factor of 1.2, which is deviated from factors close to 2, observed in literature because of reagents being from different manufacturers and running two assays on two different platforms (automated/ semiautomated). It is important to derive a factor for an ALP assay with DEA buffer to make the results comparable to IFCC recommended AMP buffer used ALP assay.
Evaluation of point-of-care testing (poct) devices for cardiac troponin i in screening patients with myocardial infarction
(College of Chemical Pathologists of Sri Lanka, 2024) Fernando, K.; Jayasekara, D.; Kulasinghe, M.; Silva, P.; Harshanee, K.G.A.T.; Bandara, S.R.R.; Dayanath, B.K.T.P.
INTRODUCTION AND OBJECTIVES Cardiac troponin I (cTnI) is a crucial biomarker for diagnosing myocardial infarction (MI). However, many remote hospitals lack access to cTnI assessment facilities. This study investigates the feasibility of using Point-of Care Testing (POCT) devices to triage MI patients in such settings, facilitating their transfer to tertiary care hospitals. Assessing the quality of POCT devices is essential for this purpose. This report outlines the assessment methodology of two POCT devices and presents the obtained results.METHODS Two POCT devices, labelled X and Y, for measuring cTnI were compared against the Ortho-Vitros 3600, serving as the reference method, with optimum internal and external quality control measures. Basic specifications of the POCT devices and the comparator were obtained from their respective kit inserts. Routine patient samples were analyzed in singlicate using POCT devices and the reference method. Linear regression analysis was conducted, and correlation graphs were generated. Within-run precision was evaluated using a patient sample and imprecision (CV) was calculated for the POCT devices.RESULTS The linearity ranges for cTnI measurement with POCT devices X and Y were 0.01–15 ng/mL and 0.03–30 ng/ mL, respectively, with decision-making cutoff values for diagnosing MI established at 0.04 ng/mL and 0.5 ng/ mL, respectively. Regression analysis demonstrated acceptable linearity for both POCT devices, with correlation of R2=0.7388 for device X and R2=0.8881 for device Y. However, higher imprecision was observed for both analyzers, with a CV of 26% for device X and 20% for device Y at decision-making cutoff levels.CONCLUSIONS This study highlights major challenges associated with the implementing POCT devices for cTnI assays in triage settings aimed at diagnosing MI in acute care. Specifically, the adoption of higher cutoff levels in the POCT devices, not aligned with the recommended 99th percentile for the healthy population, and the poor precision observed at these cutoff values emerge as significant hurdles.
Obtaining Patient Torso Geometry for the Design of Scoliosis Braces. A Study of the Accuracy and Repeatability of Handheld 3D Scanners
(Prosthetics and orthotics international, 2022) Sanz-Pena, I.; Arachchi, S.; Curtis-Woodcock, N.; Silva, P.; McGregor, A. H.; Newell, N.
Objective: Obtaining patient geometry is crucial in scoliosis brace design for patients with adolescent idiopathic scoliosis. Advances in 3D scanning technologies provide the opportunity to obtain patient geometries quickly with fewer resources during the design process compared with the plaster-cast method. This study assesses the accuracy and repeatability of such technologies for this application. Methods: The accuracy and repeatability of three different handheld scanners and phone-photogrammetry was assessed using different mesh generation software. Twenty-four scans of a single subject's torso were analyzed for accuracy and repeatability based on anatomical landmark distances and surface deviation maps. Results: Mark II and Structure ST01 scanners showed maximum mean surface deviations of 1.74 ± 3.63 mm and 1.64 ± 3.06 mm, respectively. Deviations were lower for the Peel 1 scanner (maximum of -0.35 ± 2.8 mm) but higher with the use of phone-photogrammetry (maximum of -5.1 ± 4.8 mm). The mean absolute errors of anatomical landmark distance measurements from torso meshes obtained with the Peel 1, Mark II, and ST01 scanners were all within 9.3 mm (3.6%), whereas phone-photogrammetry errors were as high as 18 mm (7%). Conclusions: Low-cost Mark II and ST01 scanners are recommended for obtaining torso geometries because of their accuracy and repeatability. Subject's breathing/movement affects the resultant geometry around the abdominal and anterolateral regions.