Browsing by Author "Mahmoud, Hamdy F. F."

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    Platelet indices parameters in the new disease activity score of rheumatoid arthritis with ankle involvement: A comparative analytic study
    Khaled, Safaa A. A.; Mahmoud, Hamdy F. F. (PLoS, 2021-09-01)
    Background: Platelet indices (PIs) are platelet parameters that are correlated with platelet activity. Despite being widely available, inexpensive, and feasible; their use in clinical settings is limited. Recently, we developed a new score (EgyDAS), which relies on PIs and assesses disease activity in rheumatoid arthritis (RA). Objectives: This study explored the practicability and validity of EgyDAS in RA with ankle involvement, considering that ankle is neglected in the commonly used DAS28 score. Methods: This comparative case-control study included 2-groups of RA patients, group1 (control): without and group 2: with ankle involvement. Results: Ankle involvement in RA showed no gender or age differences, however, it was associated with higher platelet count, erythrocyte sedimentation rate (ESR), Creactive protein (CRP), platelet distribution width (PDW), visual analogue scale (VAS), tender joint count (TJC), and lower hemoglobin (Hb) and mean platelet volume (MPV). DAS28 categorized a higher proportion of patients to have high disease activity compared with Egy- DAS; moreover, it did not detect those in remission in group 2 patients. Highly significant differences in the 2-scores were observed between the two groups. Further analyses revealed superiority of EgyDAS in assessing disease activity in group 2 patients. Finally, both scores were found correlated together in the study groups. Conclusions: Over or underestimation of RA disease activity could occur when using DAS28. PIs were found correlated with ankle involvement in RA. PIs and EgyDAS are the best tools to assess disease activity in RA patients with ankle involvement. However, the study recommended the use of both scores together.
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    Semiparametric Integrated and Additive Spatio-Temporal Single-Index Models
    Mahmoud, Hamdy F. F.; Kim, Inyoung (MDPI, 2023-11-13)
    In this paper, we introduce two semiparametric single-index models for spatially and temporally correlated data. Our first model has spatially and temporally correlated random effects that are additive to the nonparametric function, which we refer to as the “semiparametric spatio-temporal single-index model (ST-SIM)”. The second model integrates the spatially correlated effects into the nonparametric function, and the time random effects are additive to the single-index function. We refer to our second model as the “semiparametric integrated spatio-temporal single-index model (IST-SIM)”. Two algorithms based on a Markov chain expectation maximization are introduced to simultaneously estimate the model parameters, spatial effects, and time effects of the two models. We compare the performance of our models using several simulation studies. The proposed models are then applied to mortality data from six major cities in South Korea. Our results suggest that IST-SIM (1) is more flexible than ST-SIM because the former can estimate various nonparametric functions for different locations, while ST-SIM enforces the mortality functions having the same shape over locations; (2) provides better estimation and prediction, and (3) does not need restrictions for the single-index coefficients to fix the identifiability problem.
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    Semiparametric Permutation-Based Change Point Detection with an Application on Chicago Cardiovascular Mortality Data
    Mahmoud, Hamdy F. F. (MDPI, 2022-03-08)
    Climate change has several negative effects on health, including cardiovascular disease. Many studies have considered the effect of temperature on cardiovascular disease and found that there is an association between extreme levels of temperature, cold and hot, and cardiovascular disease. However, the number of articles that have studied the change point or the threshold in temperature is very limited. To the best of our knowledge, there have been no studies focusing on detecting and testing the significance of the change point in the temperature–cardiovascular relationship. Identifying the change point in cities may help to design better adaptive strategies in view of predicted weather changes in the future. Knowing the change points of temperature may prevent further mortality associated with the weather changes. Therefore, in this paper, we propose a unified approach that simultaneously estimates the semiparametric relationship and detects the significant point. A semiparametric generalized change point single index model is introduced as our unified approach by adjusting for several weather variables. A permutation-based testing procedure to detect the change point is introduced as well. A simulation study is conducted to evaluate the proposed algorithm. The advantage of our proposed approach is demonstrated using the cardiovascular mortality data of the city of Chicago, USA.
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    Significance of the mathematically calculated red cell indices in patients with qualitative and quantitative hemoglobinopathies
    Ahmed, Heba A.; Khaled, Safaa A. A.; Fahmy, Eman M.; Mohammed, Nesreen A.; Mahmoud, Hamdy F. F. (2022-08-04)
    Background Hemoglobinopathies represent a set of inherited red blood cell (RBCs) disorders, characterized by abnormal hemoglobin molecule. They include qualitative and quantitative hemoglobinopathies, with a structurally abnormal globin chain in the first and defective production in the later. This study assessed, for the first time, the significance of the mathematically calculated RBC indices to identify patients with hemoglobinopathies from normal subjects or iron deficiency anemia (IDA) and to differentiate various types of hemoglobinopathies from each other. Subjects and methods The study was a comparative hospital based and included 167 participants with hemoglobinopathies (group 1) and 49 participants with IDA (group 2) as an active comparator. Another 50 healthy volunteers (group 3) were also included. All participants were subjected to medical history, clinical examination, CBC, and HPLC. Next, 10 RBC indices were mathematically calculated from the CBC for each participant. Results Gender analysis shows that females represent 36.8% in thalassemia group, 42% in sickle cell disease (SCD) group, and 71.4% in IDA group. The receiver operating characteristic (ROC) curve shows that Ehsani index (EI) is the most reliable screening tool for thalassemics because of showing the highest Youden index and specificity of 41.88% and 88.89%, respectively, followed by Shine and Lal index (SL), with Youden index (YI) value, specificity, and sensitivity equal to 39.78%, 69.70%, and 70.09%, respectively. Similar results were found for IDA. For SCD, SL index is the most suitable screening tool. In conclusion, the mathematically calculated RBC indices are available, cheap, reliable, and sensitive tools for screening patients with hemoglobinopathies.
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    Some Advanced Semiparametric Single-index Modeling for Spatially-Temporally Correlated Data
    Mahmoud, Hamdy F. F. (Virginia Tech, 2014-10-09)
    Semiparametric modeling is a hybrid of the parametric and nonparametric modelings where some function forms are known and others are unknown. In this dissertation, we have made several contributions to semiparametric modeling based on the single index model related to the following three topics: the first is to propose a model for detecting change points simultaneously with estimating the unknown function; the second is to develop two models for spatially correlated data; and the third is to further develop two models for spatially-temporally correlated data. To address the first topic, we propose a unified approach in its ability to simultaneously estimate the nonlinear relationship and change points. We propose a single index change point model as our unified approach by adjusting for several other covariates. We nonparametrically estimate the unknown function using kernel smoothing and also provide a permutation based testing procedure to detect multiple change points. We show the asymptotic properties of the permutation testing based procedure. The advantage of our approach is demonstrated using the mortality data of Seoul, Korea from January, 2000 to December, 2007. On the second topic, we propose two semiparametric single index models for spatially correlated data. One additively separates the nonparametric function and spatially correlated random effects, while the other does not separate the nonparametric function and spatially correlated random effects. We estimate these two models using two algorithms based on Markov Chain Expectation Maximization algorithm. Our approaches are compared using simulations, suggesting that the semiparametric single index nonadditive model provides more accurate estimates of spatial correlation. The advantage of our approach is demonstrated using the mortality data of six cities, Korea from January, 2000 to December, 2007. The third topic involves proposing two semiparametric single index models for spatially and temporally correlated data. Our first model has the nonparametric function which can separate from spatially and temporally correlated random effects. We refer it to "semiparametric spatio-temporal separable single index model (SSTS-SIM)", while the second model does not separate the nonparametric function from spatially correlated random effects but separates the time random effects. We refer our second model to "semiparametric nonseparable single index model (SSTN-SIM)". Two algorithms based on Markov Chain Expectation Maximization algorithm are introduced to simultaneously estimate parameters, spatial effects, and times effects. The proposed models are then applied to the mortality data of six major cities in Korea. Our results suggest that SSTN-SIM is more flexible than SSTS-SIM because it can estimate various nonparametric functions while SSTS-SIM enforces the similar nonparametric curves. SSTN-SIM also provides better estimation and prediction.
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    Value of Platelet Distribution Width and Mean Platelet Volume in Disease Activity Score of Rheumatoid Arthritis
    Khaled, Safaa A. A.; NasrEldin, Eman; Makarem, Yasmine S.; Mahmoud, Hamdy F. F. (Dove Press, 2020)
    Background and Objective: Disease activity score 28 (DAS28) for rheumatoid arthritis (RA) is the commonly used DAS; it relies on clinical parameters that could be subjective. This work aimed to create a more accurate DAS for RA and assess its validity. Patients and Methods: The study included 98 RA patients and 53 matched controls; they were interviewed, clinically examined, their visual analogue scales (VAS) were reported, and then blood samples were withdrawn for erythrocyte sedimentation rate (ESR), complete blood count (CBC), and C-reactive protein (CRP). Platelet indices (PIs) were obtained from the CBC including Plt (platelet count), mean platelet volume (MPV), platelet distribution width (PDW) and plateletcrit (PCT). DAS28 was calculated for each patient using RheumaHelper mobile software. Minitab Statistical Package® and SPSS v20 software were used for data analysis. Results and Conclusions: Results revealed perfect matching between patients and controls as regarding age and gender. ESR, CRP and PDW were significantly higher in patients than controls; also positive correlations were detected among these variables. A new DAS for RA was developed; ESR, CRP, PDW and MPV were the components for this index. Further analyses showed that this new score was significantly higher in patients than controls and correlated with DAS28 of the patients. Furthermore the new score could identify RA patients from healthy subjects (cut off value < −0.79) and stratified RA patients according to their disease activity into low, intermediate, high, or in remission. Conclusively, we developed a more precise, easily obtained new DAS for RA. This new DAS has both diagnostic/prognostic values in patients with RA.
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    Welfare Assessment and Identification of the Associated Risk Factors Compromising the Welfare of Working Donkeys (Equus asinus) in Egyptian Brick Kilns
    Farhat, Shaaban F.; McLean, Amy K.; Mahmoud, Hamdy F. F. (MDPI, 2020-09-09)
    Donkeys are a cornerstone in human existence, having played an important role throughout history in different economic activities, such as working in brick kilns in Egypt. This study was conducted from January 2017 to the end of April 2017 in the El-Saf brick kilns, which are located to the south of the Giza Governorate and 57 Km away from Cairo. Physical clinical health and behavior data were collected from 179 donkeys spanning over a random sample of 20 brick kilns selected from the El-Saf brick kilns. Behavioral, physical health, harness, and environmental parameters were assessed and recorded. The study found that 80 ± 3% (n = 179) of kiln donkeys have some type of wound, and the most serious wound is a beating wound (49 ± 3.7%), which is caused by drivers hitting the donkeys. The drivers are mostly children, who have insufficient knowledge, skills, and attitudes to effectively communicate with their donkeys and no motivation to enhance the welfare of these equids. Other wounds are related to the harness, such as the breeching (10 ± 2.2%), saddle (43 ± 3.7%), neck collar (40 ± 3.6%), and shaft of the cart (12 ± 2.4%). A poor body condition was seen in 56 ± 3.7% of kiln donkeys. A correlation in terms of the prevalence of wounds was found between the body condition (p-value < 0.01) and/or cleanliness of the harness. There was a negative association between the body condition and wound prevalence in brick kilns (Pearson coefficient of correlation −0.71). The physical enviromental factors that affect the body condition of working donkeys are the working hours of donkeys/day, the number of donkeys in a kiln, the distance from loading to the oven, and the concentrated food/donkey (p-value < 0.01). These three variables can explain 78.85% of the variability in body conditions based on a 1–5 scale. In addition to health parameters, behavior parameters, such as the donkeys’ general attitude, reaction to observers, and chin contact are associated with the body condition (p-value < 0.01). As a consequence, it is important for the owners of working donkeys to pay attention to their body condition in order to avoid compromising their body condition and welfare.