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Sains Malaysiana 45(11)(2016): 1741–1745
New Approach to
Calculate the Denominator for the Relative Risk Equation (Pendekatan
Baharu untuk Menghitung
Pembawah bagi Persamaan
Risiko Relatif) NOR AZAH
SAMAT*
& SYAFIQAH HUSNA MOHD
IMAM
MA’AROF Department of Mathematics,
Faculty of Science and Mathematics, Universiti
Pendidikan Sultan Idris, 35900 Tanjong
Malim, Perak Darul Ridzuan,
Malaysia Diserahkan: 21 Mei 2015/Diterima: 24 Mac 2016 ABSTRACT Disease frequency is used to
measure the situation of the disease with reference to the population
size and time period which is in a fractional form. The lower
part of the fraction, known as denominator is the important part
as it was used to calculate a rate or ratio. Since the disease
frequency is based on a ratio estimator, the results are highly
dependent upon the value of denominator. Therefore, the main aim
of this paper was to propose a new method in calculating the denominator
for the relative risk equation with the application to chikungunya
disease data from Malaysia. The new method of calculating the
denominator of the relative risk equation includes the use of
discrete time-space stochastic SIR-SI
(susceptible-infective-recovered for human population
and susceptible-infective for vector population) disease transmission
model instead of the total disease counts. The results of the
analysis showed that the estimation of expected disease counts
based on total posterior means can overcome the problem of expected
counts estimation based on the total number of disease especially
when there is no observed disease count in certain regions. The
proposed new approach to calculate the denominator for the relative
risk equation is suitable for the case of rare disease in which
it offers a better method of expected disease counts estimation.
Keywords: Chikungunya disease;
disease mapping; relative risk estimation; SIR-SI disease
transmission model ABSTRAK Frekuensi penyakit digunakan
untuk mengukur
situasi sesuatu penyakit dengan merujuk kepada saiz populasi dan
tempoh masa yang berbentuk
pecahan. Bahagian
bawah pecahan,
yang dikenali sebagai pembawah ialah bahagian yang penting kerana ia
digunakan untuk
menghitung suatu kadar atau nisbah.
Memandangkan frekuensi penyakit
adalah berasaskan
suatu anggaran nisbah, keputusan anggaran sangat bergantung kepada nilai pembawah tersebut. Oleh itu, matlamat
utama kajian ini
ialah untuk
mencadangkan suatu kaedah baharu dalam
mengira pembawah
bagi persamaan risiko relatif dengan aplikasi kepada data penyakit chikungunya
dari Malaysia. Kaedah baru pengiraan
pembawah bagi
persamaan risiko relatif mengambil kira penggunaan model jangkitan penyakit stokastik diskrit masa-ruang SIR-SI (rentan-jangkitan-pulih
bagi populasi
manusia, rentan-jangkitan bagi populasi vektor)
dan bukan
jumlah bilangan penyakit. Hasil analisis menunjukkan
bahawa penganggaran
bilangan jangkaan penyakit berdasarkan jumlah posterior min dapat mengatasi masalah penganggaran jumlah jangkaan berdasarkan jumlah bilangan penyakit khususnya apabila tiada penyakit
yang diperhatikan dalam
sesuatu kawasan. Kaedah baru yang dicadangkan untuk mengira pembawah bagi persamaan risiko relatif adalah sesuai bagi
kes penyakit
yang jarang berlaku kerana ia
menawarkan kaedah
yang lebih baik bagi
penganggaran bilangan
jangkaan penyakit. Kata kunci: Model jangkitan
penyakit SIR-SI; pemetaan penyakit; penganggaran risiko relatif; penyakit chikungunya RUJUKAN
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