Tassha Hilda Adnan

Requirements for Minimum Sample Size for Sensitivity and Specificity Analysis

Sensitivity and specificity analysis is commonly used for screening and diagnostic tests. The main issue researchers face is to determine the sufficient sample sizes that are related with screening and diagnostic studies. Although the formula for sample size calculation is available but concerning majority of the researchers are not mathematicians or statisticians, hence, sample size calculation might not be easy for them. This review paper provides sample size tables with regards to sensitivity and specificity analysis. These tables were derived from formulation of sensitivity and specificity test using Power Analysis and Sample Size (PASS) software based on desired type I error, power and effect size. The approaches on how to use the tables were also discussed.

The Malaysian Cataract Surgery Registry: Cataract Surgery Practice Pattern.

PurposeTo present the cataract surgery practice pattern among the ophthalmic surgeons in hospitals managed by the Ministry of Health (MOH) in Malaysia. DesignSecondary data analysis on Malaysian Cataract Surgery Registry (CSR). MethodsThe Malaysian CSR collected data on cataract surgeries done at all the ophthalmology departments in MOH from year 2002 to 2004 (paper-based) and 2007 to 2011 (web-based). Data collected include type of admission, surgical techniques, type of anesthesia, and intraocular lens (IOL). Descriptive and inferential analysis was performed. ResultsOf the 185,388 cataract surgeries done over 8 years, 171,482 (91.5%) were captured in CSR. There was a steep rise in phacoemulsification cataract surgery from 39.7% in 2002 to 78.0% in 2011 with a corresponding fall in extracapsular cataract extraction from 54.0% to 17.3% in the respective years. This explained the surge in the use of foldable IOL from 26.5% in 2002 to 88.3% in 2011. The proportion of cataract surgery with IOL implantation was 97.5% in 2012 and 98.2% in 2011. The proportion of day-care cataract surgery was low, with 39.3% in 2002 to 52.3% in 2011. Vitreoretinal surgery was the commonest type of combined surgery performed. ConclusionsAlthough phacoemulsification was performed in two thirds of the patients who presented to MOH hospitals in Malaysia, extracapsular cataract extraction was still being performed because of a significant proportion of cataract that were brunescent and limited access to phacoemulsification machines and consumables. There is a need to increase day-care cataract surgery as it will eventually save cost.

Forecasting the Incidence and Prevalence of Patients with End-Stage Renal Disease in Malaysia up to the Year 2040

Background. The incidence of patients with end-stage renal disease (ESRD) requiring dialysis has been growing rapidly in Malaysia from 18 per million population (pmp) in 1993 to 231 pmp in 2013. Objective. To forecast the incidence and prevalence of ESRD patients who will require dialysis treatment in Malaysia until 2040. Methodology. Univariate forecasting models using the number of new and current dialysis patients, by the Malaysian Dialysis and Transplant Registry from 1993 to 2013 were used. Four forecasting models were evaluated, and the model with the smallest error was selected for the prediction. Result. ARIMA (0, 2, 1) modeling with the lowest error was selected to predict both the incidence (RMSE = 135.50, MAPE = 2.85, and MAE = 87.71) and the prevalence (RMSE = 158.79, MAPE = 1.29, and MAE = 117.21) of dialysis patients. The estimated incidences of new dialysis patients in 2020 and 2040 are 10,208 and 19,418 cases, respectively, while the estimated prevalence is 51,269 and 106,249 cases. Conclusion. The growth of ESRD patients on dialysis in Malaysia can be expected to continue at an alarming rate. Effective steps to address and curb further increase in new patients requiring dialysis are urgently needed, in order to mitigate the expected financial and health catastrophes associated with the projected increase of such patients.

The Malaysian Cataract Surgery Registry: Profile of Patients Presenting for Cataract Surgery.

PurposeTo investigate the change in the profile of patients who had cataract surgery at Ministry of Health (MOH) hospitals in Malaysia. DesignSecondary analysis on Malaysian Cataract Surgery Registry data. MethodsThe Malaysian Cataract Surgery Registry, a MOH-initiated registry, collects data on patients who had cataract surgery at the 36 MOH ophthalmology departments including demography, causes of cataract, systemic and ocular comorbidity, preoperative visual acuity (VA), operative details, and postoperative outcomes. This article reviews data on patient profiles from 2002 to 2004 and 2007 to 2011. ResultsThe coverage of cataract surgery was 91.5% (171,482/185,388). Mean patient age was 64.5 years, and 51.6% were women. A high proportion of patients had hypertension (48.9%), diabetes mellitus (37.1%), and diabetic retinopathy (10.7%). Most had senile cataract (93.4%) and one third had second eye surgery. Most patients (82.0%) had preoperative unaided VA of worse than 6/12. Eyes presenting with unaided VA of worse than 3/60 decreased from 62.6% in 2002 to 47.7% in 2011, whereas those with 6/18 to 3/60 increased from 35.2% to 48.5% (P < 0.001). Patients who had extracapsular cataract extraction had worse preoperative VA than those who had phacoemulsification (81.3% vs 40% had vision worse than 3/60). ConclusionsThe obvious change in patient profiles was the decreasing number of eyes presenting with worse than 3/60 vision. Compared with developed countries, patients who had cataract surgery at MOH hospitals in Malaysia were younger and had higher associations with diabetes mellitus and diabetic retinopathy.

Modification of systematic sampling: A comparison with a conventional approach in systematic sampling

Systematic sampling is a nonbiased method in recruitment selection process since it is a probability sampling. However, due to slow recruitment, we modified the systematic sampling and evaluate this technique in comparison with the conventional approach of systematic sampling. In this study, we compare results derived from analysis of few sub samples, with the true parameter from the population based on modified systematic sampling and conventional systematic sampling. We found that our modified systematic sampling is slightly better than conventional approach in systematic sampling.

Estimates of visual impairment and its causes from the National Eye Survey in Malaysia (NESII)

Background Population-based data on prevalence, causes of blindness and extent of ophthalmological coverage is required for efficient implementation and evaluation of ocular health programs. In view of the scarcity of prevalence data for visual impairment and blindness in Malaysia, this study aims to estimate the prevalence and causes of visual impairment (VI) in the elderly, using Rapid Assessment of Avoidable Blindness (RAAB) survey technique. Methods Malaysia was divided into six regions, with each region consisting of 50 clusters. Multistage cluster sampling method was used and each cluster contained 50 residents aged 50 years and above. Eligible subjects were interviewed and pertinent demographic details, barriers to cataract surgery, medical and ocular history was noted. Subjects had visual acuity assessment with tumbling ‘E’ Snellen optotypes and ocular examination with direct ophthalmoscope. The primary cause of VI was documented. Results were calculated for individual zones and weighted average was used to obtain overall prevalence for the country. Inter-regional and overall prevalence for blindness, severe VI and moderate VI were determined. Causes of VI, cataract surgical coverage and barriers to cataract surgery were assessed. Results A total of 15,000 subjects were examined with a response rate of 95.3%. The age and gender-adjusted prevalence of blindness, severe visual impairment and moderate visual impairment were 1.2% (95% Confidence Interval: 1.0–1.4%), 1.0% (95%CI: 0.8–1.2%) and 5.9% (5.3–6.5%) respectively. Untreated cataract (58.6%), diabetic retinopathy (10.4%) and glaucoma (6.6%) were the commonest causes of blindness. Overall, 86.3% of the causes of blindness were avoidable. Cataract surgical coverage (CSC) in persons for blindness, severe visual impairment and moderate visual impairment was 90%, 86% and 66% respectively. Conclusion Increased patient education and further expansion of ophthalmological services are required to reduce avoidable blindness even further in Malaysia.

Catquest-9SF questionnaire: validation of Malay and Chinese-language versions using Rasch analysis

BackgroundCatquest questionnaire was originally developed in Swedish to measure patients’ self-assessed visual function to evaluate the benefit of cataract surgery. The result of the Rasch analysis leading to the creation of the nine-item short form of Catquest, (Catquest-9SF), and it had been translated and validated in English. The aim is therefore to evaluate the translated Catquest-9SF questionnaire in Malay and Chinese (Mandarin) language version for measuring patient-reported visual function among cataract population in Malaysia.MethodsThe English version of Catquest-9SF questionnaire was translated and back translated into Malay and Chinese languages. The Malay and Chinese translated versions were self-administered by 236 and 202 pre-operative patients drawn from a cataract surgery waiting list, respectively. The translated Catquest-9SF data and its four response options were assessed for fit to the Rasch model.ResultsThe Catquest-9SF performed well in the Malay and Chinese translated versions fulfilling all criteria for valid measurement, as demonstrated by Rasch analysis. Both versions of questionnaire had ordered response thresholds, with a good person separation (Malay 2.84; and Chinese 2.59) and patient separation reliability (Malay 0.89; Chinese 0.87). Targeting was 0.30 and −0.11 logits in Malay and Chinese versions respectively, indicating that the item difficulty was well suited to the visual abilities of the patients. All items fit a single overall construct (Malay infit range 0.85–1.26, outfit range 0.73–1.13; Chinese infit range 0.80–1.51, outfit range 0.71–1.36), unidimensional by principal components analysis, and was free of Differential Item Functioning (DIF).ConclusionsThese results support the good overall functioning of the Catquest-9SF in patients with cataract. The translated questionnaire to Malay and Chinese-language versions are reliable and valid in measuring visual disability outcomes in the Malaysian cataract population.

The Malaysian Cataract Surgery Registry: risk Indicators for posterior capsular rupture

Aim To identify the risk indicators for posterior capsular rupture (PCR) in the Malaysian Cataract Surgery Registry (CSR). Methods Data from the web-based CSR were collected for cataract surgery performed from 2008 to 2013. Data was contributed by 36 Malaysian Ministry of Health public hospitals. Information on patients age, ethnicity, cause of cataract, ocular and systemic comorbidity, type of cataract surgery performed, local anaesthesia and surgeons status was noted. Combined procedures and type of hospital admission were recorded. PCR risk indicators were identified using logistic regression analysis to produce adjusted OR for the variables of interest. Results A total of 150 213 cataract operations were registered with an overall PCR rate of 3.2%. Risk indicators for PCR from multiple logistic regression were advancing age, male gender (95% CI 1.04 to 1.17; OR 1.11), pseudoexfoliation (95% CI 1.02 to 1.82; OR 1.36), phacomorphic lens (95% CI 1.25 to 3.06; OR 1.96), diabetes mellitus (95% CI 1.13 to 1.29; OR 1.20) and renal failure (95% CI 1.09 to 1.55; OR 1.30). Surgical PCR risk factors were combined vitreoretinal surgery (95% CI 2.29 to 3.63; OR 2.88) and less experienced cataract surgeons. Extracapsular cataract extraction (95% CI 0.76 to 0.91; OR 0.83) and kinetic anaesthesia were associated with lower PCR rates. Conclusions This study was agreed with other studies for the risk factors of PCR with the exception of local anaesthesia given and type of cataract surgery. Better identification of high-risk patients for PCR decreases intraoperative complications and improves cataract surgical outcomes.