Epidemiological Tools

Epidemiological Tools

There are a variety of tools that an epidemiologist might have at his or her disposal. The most common tools that are used in the field are SAS, SPSS, EpiInfo, R, and many others. These require significant time and diligence to become proficient at each of these statistical tools. However, almost every office has Microsoft Excel, Numbers (the Mac equivalent), or Google’s Excel-like product.

Often times, epidemiological calculations can seem/appear intimidating. However, if you let the excel document do the work for you then you do not have to worry about making errors in simple math. Please download the attached Microsoft Excel spreadsheet. You will be doing the following:

Calculating:

• Crude Mortality Rate
• Age-Specific Mortality Rate
• Age-Adjustment (using the direct method)
• Prevalence 
• Incidence Density

Graphing:

• Incidence and Prevalence

You will need to go to the

Census Bureau

(https://data.census.gov/) then click on Advanced Search then click on Geography. In the area marked state, county, or place, type your community or a community near you and select enter. You are going to want information from a table that contains Age and Sex in the title. 

Please see attached file

Morbidity Measures

Pop

1

200

400

200

100

Year
Number Sick
Total Pop
Incidence
Prevalence

900

400

200

400

																																		Example: Open Cohort (City, State, Zip Code etc)
	Year		Number Sick					Total		Incidence		Prevalence
			200		900	890,750	101.0			4	101.0384507438
2002				400	908,830	44.01	143.0410527821
2003	920,6			23	21.72	162.9331441861
2004	930,517	42.99	204.1875645474
2005		100	939,605	10.64	212.855402004
2006	300	948,844	31.62	242.4002259592
2007	600	956,749	62.71	303.1098020484
2008	963,160	20.76	321.8572199842
2009	975,122	10.26	328.1640656246
Problem !: Open Cohort	This is the space where you should place your chart!
2012
2013
2014
2015

Formulas in Excel can be useful. Most epidemiological measures of incidence and prevalence are simple formulas that you can program in excel. Please visit this Microsoft Overview:

https://support.office.com/en-us/article/overview-of-formulas-in-excel-ecfdc708-9162-49e8-b993-c311f47ca173

Once you have finished the material, you will be ready for our first step. Incidence and Prevalence. The generic formula for both incidence and prevalence is sick/total population x some population multiplier, which can range from 100, 1,000, 10,000, 100,000, or even 1,000,000.

https://support.office.com/en-us/article/overview-of-formulas-in-excel-ecfdc708-9162-49e8-b993-c311f47ca173

Figure 1: Incidence and Prevealence of Herpes 2001 – 2009

Incidence 2001.0 2002.0 2003.0 2004.0 2005.0 2006.0 2007.0 2008.0 2009.0 101.0384507437553 44.01263162527646 21.72441922480755 42.98685569420011 10.64277010020168 31.61742077728267 62.712372837599 20.76498193446572 10.25512705076903 Prevalence 2001.0 2002.0 2003.0 2004 .0 2005.0 2006.0 2007.0 2008.0 2009.0 101.0384507437553 143.0410527821485 162.9331441860566 204.1875645474505 212.8554020040336 242.4002259591672 303.1098020483951 321.8572199842186 328.164065624609

Years

Rate Pper 100,000 Population

In this example, let’s assume that once you are infected with this disease you have it for life. Also, a fundamental assumption of this table will be that no one dies in this 9 year time window.
Click on each incidence and prevalence window to see where I inserted the formula.
Incidence = (Number Sick Cell/TotalPopulation Cell)*100,000
Prevalence is a little more different. Because people do not die from this disease and for this example, no one is dieing we have to add the previous years numbers for total diseased.
If we were trying to calculate the prevalence for 2002, we would have to enter the number from 2001 + 2002. Please click on the cell to see how I wrote the formula.

In the chart above, please find the population data from your town for the years 2012-2013. Using Excel formula complete the table. Once your table is complete, please visist the following link:
https://support.office.com/en-us/article/create-a-chart-from-start-to-finish-0baf399e-dd61-4e18-8a73-b3fd5d5680c2#OfficeVersion=Windows
You will need to create a chart based on the data you generated. Please see my example to the right of these instructions.

Mortality Measures

& Age Specific Rate (

)

ASR

4

23

231,158

231,158

Total

Crude Mortality Rate

are calculated by multiplying the raw ASR X Standard Pop

Age Group
Deaths
Total Population

Expected Deaths

0 – 14
4
231,158

15 – 19
23
73,200

20 – 34
500
231,158

35 – 54
250
231,158

55+
1000
211,895

Total
1777
978,569

= Expected Deaths / Standard Population x 100,000

Adjusted Mortality Rate

Age Group
Deaths
Total Population
ASR*

Expected Deaths

0 – 14
4
231,158
0.000017304
15 – 19
23
73,200
0.000314208
20 – 34
500
231,158
0.002163023
35 – 54
250
231,158
0.001081511
55+
1000
211,895
0.004719319

Total
1777
978,569

Adjusted Mortality Rate

Example 1:	Crude Mortality Rate	ASR
		Age Group			Deaths			Total Population
		0 – 14									231,158	1.73
		15 – 19			73,200	31.42
		20 – 34			500	216.30
		35 – 54			250	108.15
		55+			1000			211,895	471.93
		1777			978,569
181.59
Example 2: Age-Adjusted Rate (Direct Method)			Expected Deaths
	ASR*	Standard Population ^
	0.000017304	56,100,000.00	970.76
	0.000314208	23,100,000.00	7258.20
	0.002163023	69,300,000.00	149897.47
	0.001081511	85,800,000.00	92793.67
	0.004719319	92,400,000.00	436065.03
326,700,000.00	686985.14
* we leave the ASR in decimal form and do not multiply it by 100,000 for this method
^ the standard population is usually the standard population for the United States.
However, it can really be whatever population you want it to be.
		Adjusted Mortality Rate
210.28
Your job is to use the Example 2 chart except for the standard population. Replace the standard population
data with data points from the American FactFinder.	Then calculate the adjusted rate.
Your Population

In this exercise, we will be exploring how to calculate crude mortality, age-specific mortality, and direct age-adjustement. This exercise will require you to have access to demographic data from American FactFinder. Please work on the morbidity assignment prior to tackling this assignment. I am going to assume you already know how to use Excel formulas, as they were used extensively in the morbidity tab.
As with the previous tab, I will provide you examples. Remember:
Age Specific Mortality (ASR): Total Died in that Age Category/Total in that Age Category x 100,000
Crude Mortality Rate: All deaths/Total Population x 100,000
Age-adjustment is odd, you have to calculate the ASR first and not multiply it by 100,000. Then you multiply it by a standard population, or a population you are attempting to compare it to.

Now if you look at the ASR, you will see that clearly 55+ have the highest age specific rate. However, remember that population covers a lot of people and can be prone to a high rate or mortality already.
Calculating an age specific adjustment be useful to see if the crude rate increases or decreases.

http://sphweb.bumc.bu.edu/otlt/MPH-Modules/EP/EP713_StandardizedRates/EP713_StandardizedRates_print.html