A major advantage of EDC is that data become available after collection in the field without delay. This enables EDC users to monitor data collection, evaluate the study status and to review and analyse data in real-time.
So far the literature is mainly descriptive when comparing EDC to the conventional paper method. Analytic studies usually compare the transcription (CRF-to-database) error rates for two different devices such as for example a laptop and a handheld device.
This study confirms that after a short period of EDC introduction, electronic data capture can be more time effective than the standard, paper-based data capturing process followed by double entry and verification, although the duration for the interviews using the standard paper questionnaire were shorter compared to the interviews, in which the data was collected electronically.
The second advantage, which has been described in the literature, that electronic data capture is more accurate than the paper-based method could not be confirmed in this pilot study. Even though the interviewers familiarised themselves with the new data capturing methods very quickly and the overall error rate decreased considerably over time for all EDC. For two EDC methods (tablet PC and netbook) error rates approached those of the standard method, but were never lower. In addition, since the main objective of this pilot study was to test if EDC was feasible and to explore which EDC method(s) proved to be the most suitable for the next step of field studies, range and consistency checks to optimize data quality were not implemented.
It should be noted that text fields were overrepresented in the applied questionnaire due to sample size considerations. The 2010 Demographic and Health Survey (DHS) model household questionnaire 
, or the 2010 Multiple Indicator Cluster Survey (MICS) household questionnaire 
comprised roughly 5 or 11% ‘text field’ questions, respectively, depending on household size. The most prevalent type of question in the DHS or MICS surveys was the single select type. Errors in text fields were based on exact comparisons, other than case, which might have resulted in an overestimation of the error rate for character based data, since some text field errors might have been of minor importance. For example, the misspelling of names is usually inconsequential due to unique identifiers. On the other hand this pilot study was not sufficiently powered to detect small differences in data accuracy within scales which might be important for large field studies. Direct comparison of the performance of the PDA with the remaining EDC devices is limited since a different, web based application was used for the PDA. High error rates for this device in the first week could be explained by the high proportion of missing values due to the partial loss of data. In OpenClinica® the required fields feature was implemented but not in the web based application, which might account for higher error rates for the PDA in general. The relatively poor performance of the telephone interviews is most likely due to miscommunication. Administering the questions via telephone might also have increased the interview duration since questions/answers had to be repeated more often than in face to face interviews. Interviewers improved rapidly with respect to i) the time needed to conduct the interview ii) to record the information electronically and iii) data accuracy. Since the study was designed as a pre -study for the duration of three weeks with a brief training phase, we can not judge if the interviewers had reached their highest level of performance, or if further significant improvement could be achieved. A field study would require a more intensive/longer training where a pilot phase is standard procedure. Another important consideration is whether field workers would be able to maintain their performance in the field. Comparing data accuracy for the EDC and conventional data capture process should certainly be part of follow up studies in the field, which are appropriately designed to address this question with respect to samples size and study duration.
A commonly-raised question about the feasibility of EDC in a setting like The Gambia is acceptance among field workers and whether they are capable of handling the electronic devices and software for electronic data capture. With the random selection of 6 (5 interviewers & 1 reserve) of the 12 workers nominated by the four MRC programs (Bacterial Diseases, Viral Diseases, Malaria and Nutrition), we sought a group of interviewers representative in their age, gender, work experience and performance, computer legacy, and attitudes towards EDC. Although fieldworkers were ultimately selected randomly, each programme purposely nominated three candidates and selection bias can not be ruled out completely.
At the beginning of the training session for this study, 5 out of 6 interviewers stated that EDC would be appreciated by the MRC field workers and that, since field workers have established a very good relationship with their study participants in the past, the participants would likely embrace EDC. The field workers/nurses who participated in this study were keen to learn new techniques and develop themselves further.
The majority of the interviewers would prefer the ‘bulkier’ devices, netbook and laptop, which were used for electronic data capture during the telephone interviews, to the smaller devices tablet PC and PDA for field work. That older people find it more satisfactory to use the ‘bulkier’ devices with a keyboard rather than the smaller pen-based devices has already been described in the literature 
. The display of the QWERTY keyboard on the screen of a palm-size computer results in each key being very small. This slows performance 
and may also give rise to legibility problems with difficulty in discriminating between some letters such as ‘u’ and ‘v’. The limited screen space also results in a lack of gaps between adjacent keys. This necessitates fine motor control by those making entries. The space available on the screen is very small so that the keyboard often requires the use of special function keys to access certain numeric and punctuation characters. It has long been known that moded styles of interaction can be confusing for users 
. All interviewers in our study were already familiar with the standard keyboard and had at least two years MRC work experience; each also accessed their MRC e-mail account at least once a week. The familiarity with the keyboard enabled the interviewers to enter data within a shorter time period after training compared to devices which required use of a pen. Another reason given for preferring the bulkier devices was that the larger screen allowed working with larger font sizes. Some of the field workers, especially the older ones, had problems with their eyesight. During the study interviewers would only use their glasses when the font size became so small that they could not cope otherwise. In the Gambian setting reluctance to the use of glasses is common. While two fieldworkers had problems reading text on the PDA and the tablet PC, prompting one of them to use his glasses, no such problems occurred with the netbook or the laptop. Nevertheless, in this study the use of the pen/touch screen improved rapidly for all fieldworkers , so that in the final week the duration of the interviews using OpenClinica® as the front end, which did not depend on the network connection, was in a similar range, regardless if a keyboard or a pen/touch screen was used.
Studies of performance with normal size keyboards have shown that although older people are slower in key tapping and in selecting the key to tap 
, especially if they are unskilled typists 
, there is no loss of accuracy. Given sufficient experience with the task there is evidence that older people may be able to use compensatory strategies to maintain their performance 
. This study lends support to this statement, since accuracy was not associated with age. Speed was highly associated with age, however. Younger interviewers conducted the interviews in less time than their older colleagues. As one would expect, interviewers with more experience in fieldwork were superior with respect to accuracy than those with less fieldwork experience.
Despite the availability of diverse data management software applications, it was beyond the scope of the study to test each implementation for compatibility with specific EDC tools. The data management unit at the MRC routinely supports 10 simultaneous clinical (phase I or II) and research trials; to be of practical relevance, EDC tools must be capable of supporting the commonly used software platforms. The open source, clinical trials software for EDC and clinical data management OpenClinica® was used for three of the four EDC methods, since this clinical informatics system has been designed to support GCP standards. Unfortunately an OpenClinica® version for PDAs was not available and a web based system was established. The PDA is at a disadvantage in this regard as coding a bespoke solution or integrating an open source/commercial application is time consuming and potentially expensive if commercial software is used.
At the MRC in the Gambia various types of field based epidemiological studies are conducted apart from clinical trials. For those studies alternative data capturing methods such as improved web based systems or telephone interviews in combination with EDC, or standard data collection on paper followed by optical character recognition (OCR) might be more appropriate or more cost effective.
Obvious rules, which apply for telephone interviews in general and can be found in many standard epidemiological text books, will be valid for telephone interviews in which data is collected electronically as well. For short follow up studies, in which a physical examination of the interviewee is not needed, telephone interviews might be a quick and cheap alternative to sending a field worker to the field, especially since the Gambia enjoys excellent mobile phone coverage.
A South African group recently described a web based system using standard mobile phones for electronic data capture 
. The questionnaire was developed in a word processor and sent to a standard mobile phone, which was used to collect the data during a survey. The data was stored as a text file and whenever the network connection was available, the encrypted information was sent via SMS to the host computer. The automated data upload from the mobile phone to the server reduces data loss due to damage , theft or loss of the device. Mobile phones have the advantage, that they are available, cheap, relatively robust and less attractive targets for theft compared to the more expensive devices tablet PC and netbooks. The downside of this method is, that techincal problems with data upload and download 
, electrical interference with telephone lines 
and considerable problems with the synchronization process 
have been encountered in the past.
In May 2010, a new web services framework became available in OpenClinica®, which supports mobile devices as a means of data collection for clinical trials 
For surveys, with a high percentage of tick questions can be developed, the OCR might be the appropriate choice.
EDC gives scope for applications in combination with additional functions such as GPS for identification and retracing of households, probability sampling for household surveys, which results in statistically valid samples, rapid aggregation, analyses, and availabitlity of preliminary results within days of completing the field work 
, or barcode reading to identify study subjects or samples.
EDC promises to expedite the availability of accurate data for the research program. However, there are considerable risks in achieving this goal. Pens might be lost, devices might be defective, broken or stolen. Especially in a setting like the Gambia devices are exposed to dust and humidity, and are transported on motorbikes during the day to day routine. Malfunction or loss of the device might imply that the data won't be collected according to schedule, or that data which have been already collected might be lost or have to be collected again. This will rapidly increase the time spent on gathering such information and error rates are likely to increase. For this situations a rescue plan should be established, which might involve provision of a replacement device, which will be readily available within a short period of time. Longer study duration and replacement of devices are associated with increased costs.
A good study design is important and helps to identify the variables, which are essential to meet the objective of a study. Focused and accurate data collection will increase study efficiency.
When properly designed, EDC solutions can offer a convenient, cost-effective approach for data entry, management data and reporting. Major challenges for EDC are the potential loss of the source documents, disruption of the data processing due to inappropriate human operation or inadequate maintenance of the computerized system and the need for suitable storage and maintenance of electronically captured data in a repository to make data readily available.
Before implementation in the field in a wide range of studies, one should use the results from this pilot study to develop EDC further and test this improved EDC method in the field. During the field study other factors like battery life, functionality of the devices under field conditions (dust, humidity, and transport on motorbikes) will have to be assessed. It will be essential to compare the results to the conventional paper format with respect to speed, error rate and costs. A pilot study or an extended training phase before the start of the actual study would be recommendable. This will help to identify potential major difficulties, and will give the fieldworker the opportunity to learn how to troubleshot common problems.
Abandoning paper-based systems will require not only new technologies, but additionally new work processes. This pilot study shows, that single select questions have much lower error rates compared to free text and date fields. In order to archive highly accurate data with EDC, questionnaires should be designed to maximise the use of single select or multiple choice questions and minimise the number of text and date fields. In this pilot study date fields were associated with significantly high error rates for two devices using OpenClinica® data capture compared to the web based system (PDA). OpenClinica® provides a calender function for entering dates. If the interviewer chooses to use this function, she/he markes the date on a small calender, which pops up next to the date field. The interviewers, who used this function had significantly increased error rates in the date fields, whereas the error rates for other fields such a text or single select fields for these interviewers were not increased. Dates were usually shifted one or two months or years forwards or backwards, which indicates that the interviewer missed the correct field, when choosing the date. Since the calender function seemed to be associated with increased error rates, alternative methods such as separate fields for day, month and year, should be implemented.
The introduction of EDC requires programming and data base development capacity. At the time the study was conducted OpenClinica® had no branching or skip logic implemented, but development and implementation of branching logic is crucial to reduce the error rate for missing fields. The skip logic is now available with the new OpenClinica® 3.1 beta version 
The importance of the user friendliness and quality of training materials for an EDC system was recently described to outweigh the features and functionality for small scale clinical trials 
. Interviewers should receive thorough training and retraining to improve accuracy. A practical approach might be to train a group of capable field workers/nurses, who could supervise other field workers and give support during field work. Field workers should have access to rapid trouble shooting. For trouble shooting one could implement a stepwise procedure. An interviewer might be equipped with a manual guiding the interviewer to solve some common problems by him/herself. He/she should have access to a more experienced colleague, who might be able to assist when the interviewer can't solve the problem. For more difficult problems a data base developer/programmer should be available for in depth troubleshooting.
To improve data quality it might be an advantage to offer ophthalmological examinations to the interviewers and to emphasize the benefits of wearing glasses in general and how it would positively influence the day to day work.
This study was conducted under controlled conditions, in which interviewers were supported by experienced data base programmers/developers and OpenClinica® experts, without any delay, whenever a problem arose. Aspects such as battery life, longevity of the electronic devices under field conditions (dust, humidity and frequent transport on motorbikes) and synchronization of data bases have not been addressed. The next step would be to further improve the electronic data collection method (optimized ‘work process’ for EDC with respect to questionnaire and data base design, introduce branching logic in OpenClinica®, chose the optimal device for the field work) and use an EDC method in parallel to the standard data collection method in an actual field study. Electronic devices should be selected with care with respect to brightness, size of screen, battery life and performance of the touch screen. Since EDC devices would be exposed to heat, dust and humidity, and have to be transported frequently in the field, ruggedized EDC devices might prove superior for the day to day routine. If the initial higher investment in such devices pays off in the end and guarantees fieldwork to run smoothly, might be worthwhile to be investigated in the future.
This pilot study shows that MRC field workers and nurses would be able to handle electronic devices and software for EDC, with appropriate training, retraining and adequate support during their field work. The tablet PC and the netbook with OpenClinica® as the front end performed better than the PDA and the telephone interview. Interviewers preferred the ‘bulkier’ netbook devices with a keyboard compared to the tablet PC/pen/touchpad combination for data entry.
In summary, if EDC is well designed and introduced with care, and work processes are adjusted to EDC, it will become a more time effective, potentially more accurate, and therefore cost effective method than the standard paper-based data collection method.