A time-series analysis of notified TB incidences from 2017 to 2019 was conducted and a total of 6237046 incidences were reported over the years in the entire States and the Union territory of India. An average of 173251 TB incidence per month was reported. According to the Central Tuberculosis Division (CTB), Government of India, the annual notified TB incidence rate was 156 cases per 100000 population over the years. The highest notified incidence rate was observed in Chandigarh and Delhi with an annual case detection rate as 475 and 417 cases per 100000 population respectively. The notified TB incidence rate for the Indian States and Union Territories are given in Table 1 and also represented through the map of India Fig. 5. The average marginally increasing trend was 12.05% from the years 2017 to 2019 in India. During the study period, seasonal variation revealed March, April, May to be the peak months with incidence rates as 12.13%, 12.15%, 12.15% per 100000 populations respectively. The additive decomposition for the TB incidence series revealed that the seasonal pattern changed every 12 months Fig. 2with the peak values in March, April, and May. Therefore, the notified TB incidence has shown that the seasonal trend is involved in seasonal indices.
Table 1
Annual case detection rate per 100000 population in Indian states during 2017 to 2019
S. No
|
States & UTs
|
Rate/100000 Population
|
1
|
Andaman & Nicobar Islands
|
150
|
2
|
Andhra Pradesh
|
172
|
3
|
Arunachal Pradesh
|
206
|
4
|
Assam
|
177
|
5
|
Bihar
|
92
|
6
|
Chandigarh
|
475
|
7
|
Chhattisgarh
|
144
|
8
|
Dadra and Nagar Haveli and Daman and Diu
|
148
|
9
|
Delhi
|
417
|
10
|
Goa
|
141
|
11
|
Gujarat
|
222
|
12
|
Haryana
|
206
|
13
|
Himachal Pradesh
|
221
|
14
|
Jammu & Kashmir
|
81
|
15
|
Jharkhand
|
132
|
16
|
Karnataka
|
127
|
17
|
Kerala
|
70
|
18
|
Ladakh
|
123
|
19
|
Lakshadweep
|
41
|
20
|
Madhya Pradesh
|
193
|
21
|
Maharashtra
|
161
|
22
|
Manipur
|
84
|
23
|
Meghalaya
|
144
|
24
|
Mizoram
|
226
|
25
|
Nagaland
|
193
|
26
|
Odisha
|
117
|
27
|
Puducherry
|
223
|
28
|
Punjab
|
169
|
29
|
Rajasthan
|
189
|
30
|
Sikkim
|
211
|
31
|
Tamil Nadu
|
156
|
32
|
Telangana
|
151
|
33
|
Tripura
|
62
|
34
|
Uttar Pradesh
|
177
|
35
|
Uttarakhand
|
193
|
36
|
West Bengal
|
105
|
The SARIMA model was applied to the time-series data of notified TB incidences with the characteristics of seasonal tendency. Based on the autocorrelation function plot and partial autocorrelation function plot the key parameters (p, P, d, D, q, Q) of the SARIMA Model were selected Fig. 4. The best model was generated from notified TB incidence data after applying auto.arima() function, was SARIMA (1, 0, 0)(1, 1, 0)12 where 12 is monthly time series data. The most preferred model was selected based on minimum values of AIC and BIC. The result is summarized in Table 2. The estimates and standard error of SARIMA (1, 0, 0) (1, 1, 0)12 model parameters and their significant values are given in Table 2.
Table 2
Estimates Parameter and their testing results of the SARIMA model
Measurements
|
Models
|
Estimates
|
Standard Error
|
z - Value
|
p-Value
|
Non-Seasonality
|
Ar1
|
0.4267
|
0.1981
|
2.1531
|
0.05
|
Seasonality
|
Sr1
|
-0.7452
|
0.1350
|
-5.5172
|
0.00
|
Coefficient
|
|
2272.9359
|
178.6762
|
12.7210
|
0.00
|
In the SARIMA-NNAR hybrid model, the hybrid model NNAR (3, 1, 2)12 was obtained by using nnetar and forecast.nnetar function on time series data of the notified TB incidence. The simulation accuracy of the NNAR model was determined by applying a smoothing factor (α) from the range 0.1 to 1.0. The lowest ME, RMSE, MAE, MPE, MAPE, MASE values were obtained in the hybrid model at the smoothing factor α = 0.1.
SARIMA (1, 0, 0)(1, 1, 0)12 was compared with the SARIMA-NNAR (3, 1, 2)12 hybrid model, and goodness of fit was predicted. The values for ME, RMSE, MAE, MPE, MAPE, and MASE for the hybrid model were 16.224, 5260.359, 3910.648, -0.077, 2.080, and 0.140 respectively, which is lower than the single SARIMA model having the values for the ME, RMSE, MAE, MPE, MAPE, and MASE to be 311.885, 6712.889, 4863.659, 0.033, 2.644, and 0.175 respectively given in Table 3. Finally, the monthly incidence of TB was predicted for 2020 using SARIMA and Hybrid models and compared with the actual notified TB incidences as given in Table 4. All the accuracy evaluation parameters of the hybrid model were found to be lower than the single SARIMA model and gave prediction closer to the actual TB incidences reported in 2020. However, forecast and prediction of the earlier model curves Fig. 6 & Fig. 7show that monthly TB incidence of India is showing marginally increasing trend having the seasonal effect of notified TB incidences. A seasonal pattern showing the higher TB incidence in March, April, and May was also observed. We found that yearly notified TB incidence in India shows a marginally increasing trend.
Table 3
Comparisons of Predictive Performance Measures Among scale-dependent errors on both models
Models
|
ME
|
RMSE
|
MAE
|
MPE
|
MAPE
|
MASE
|
SARIMA
|
311.885
|
6712.889
|
4863.659
|
0.033
|
2.644
|
0.175
|
SARIMA-NNAR
|
16.224
|
5260.359
|
3910.648
|
-0.077
|
2.080
|
0.140
|
Table 4 Comparison between the reported notified TB incidence and forecast of TB incidence cases for 2020
|
|
Forecast Notified TB Incidence
|
Time
|
Reported TB Cases
|
SARIMA
|
SARIMA-NNAR
|
January 2020
|
197092
|
205656.7
|
216650.8
|
February 2020
|
213898
|
208842.5
|
211051.6
|
March 2020
|
169335
|
233244.1
|
226817.5
|
April 2020
|
83705*
|
248195.1
|
221273.8
|
May 2020
|
120825
|
258247.4
|
224473.4
|
June 2020
|
157368
|
241365.6
|
209595.4
|
July 2020
|
140941
|
239259.0
|
217260.0
|
August 2020
|
121920
|
222112.5
|
198533.3
|
September 2020
|
140891
|
223292.4
|
210521.8
|
October 2020
|
150639
|
228686.0
|
198387.6
|
November 2020
|
141650
|
216776.7
|
213780.0
|
December 2020
|
176641
|
217428.1
|
196691.8
|
*Due to COVID-19 all the OPD were not functioning properly therefore notified TB data becomes decline.