Data Collection Methods

Before collecting data, it is important to answer the following questions:

◾ What do you hope to accomplish by collecting data? ◾ How will the data be collected? ◾ Who will collect the data and for how long? ◾ Where will the data be collected? ◾ What data collection instrument will be used? ◾ Is the data available? ◾ If the data is historical, in what format is it currently stored? ◾ How much disruption will data collection create? ◾ Will training be required for the people collecting or extracting the data? ◾ How much data is needed? ◾ How will the data be analyzed? ◾ Is the data adequately stratified? ◾ What is the cost of collecting the data? ◾ Is the cost of collecting data justified?

It is necessary to determine whether the data will have to be collected retrospectively or prospectively. When data is drawn from historical medical records, the process is called retrospective data collection. Conversely, data can be sampled prospectively by collecting it from current patients as they present for treatment on the day of the study visit. Collecting data retrospectively requires going into the past; that is, the data has already been collected and is available for use. Collecting data prospectively entails collecting data from this moment forward. It is common practice to collect data on prescribing encounters using both methods; however, patient care indicators often require the collection of prospective data. One of the key challenges in deciding between retrospective and prospective data is whether adequate sources of retrospective data exist. Possible sources of retrospective data can include chronological clinic visits, treatment records kept by individual providers, and drug prescription records kept at the health facility. Retrospective data sources must fulfill the following requirements: (1) a clearly defined method of selecting a random sample of patient encounters that occurred within a specified time period, (2) the exact names and definitions of all relevant variables, and (3) the proper sample size of encounters to examine.

Retrospective data is usually easier to collect than prospective data, and it is subject to fewer potential biases. It is often possible to define a