1. Mother and Child Health: Research Methods
G.J.Ebrahim
Editor
Journal of Tropical Pediatrics, Oxford University Press.
Mother and Child Health: Research Methods is published by Book - Aid, a charity publisher devoted to producing low cost texts for the developing countries. The book is based on a course developed by the author in 1978 for students attending the Master of Science programme in Mother and Child Health at the Institute of Child Health, London. The book guides the reader through the intricacies of developing research questions, designing appropriate studies to answer the questions, analysis and interpretation of the data, and the common pitfalls in conducting research studies.
The visuals and handouts used for the course participants are now being made available by the generosity of Oxford University Press (OUP), and are freely available for downloading. The full text of the book is also available on the website of OUP and the Journal of Tropical Pediatrics, but requires the password for entry. If you are a subscriber, you have the password. If your institution subscribes to the Journal the password may be obtained from your institute’s librarian.
This set of slides relates to Chapter 5 - Types of Studies -I. Descriptive Studies: Case Reports, Case Series, Cross-sectional Studies.
Mother and Child Health: Research Methods can be obtained directly from the publisher (Book - Aid, 3 Hitherwood Drive, London S.E.19 1XA), or by writing to the author at the Institute of Child Health, 30 Guilford Street, London W.C.1N 1EH. The price of the book is £6.50 plus postage and packing.

2. Preparing Case Series
All cases admitted in the time period must be included. One needs:
Precise Inclusion and exclusion criteria
What intervention was carried out for each patient, their progress and the outcome.
Influence of all variables should be accounted for.
Follow a pre-planned protocol. Give thought to how missing values, drop-outs and out-migration are to be handled.
Temporal drift is a constant danger if series need to be collected over a long time.

3. Cross-sectional Studies
Cross-sectional studies are studies of prevalence. Proportion with an attribute or disease / Number of subjects = Prevalence.
3 important questions to consider:
Definition of Case
Definition of the Population
Are cases and non-cases from an unbiased sample of the population?

4. Preparing Cross-sectional Studies
In Cross-sectional studies think of:
Sampling Procedures.
Clear definition of Target Population.
Clear definition of outcome.
Clear definition of risk factors.
Remember Confounders.
Remember seasonal variations.

5. Advantages and Disadvantages of Cross- sectional Studies
Useful for descriptive studies
Rapid, inexpensive, can provide analytic clues.
Less prone to error about exposure recall and bias
Disadvantages
Unable to sort out what came first exposure or outcome
Prone to sample distortion bias.

6. Main uses of Cross-sectional Studies
Identify and describe a problem.
Collect information for planning e.g. surveys of immunisation, antenatal care, coverage.
Evaluate utilisation rates of services.
Monitoring health status of a community by regular repeated surveys.

7. Using Cross-sectional Studies for Hypotheses Formulation
Method of Difference.
If frequency of a disease is markedly different between two groups then it is likely to be caused by a particular factor that differs between them.
Method of Agreement.
If a factor commonly occurs in which a disease occurs with high frequency then the factor is very likely associated with the disease.
Concomitant variation. Frequency of a factor varies in proportion to frequency of disease.

8. Surveys Surveys are a form of cross-sectional studies used for:
Assessing attitudes, opinions or beliefs
To study characteristics of populations regarding behaviour e.g. health service utilisation; drug use; smoking; alcohol consumption etc.
Information about socio-demographic characteristics

9. Modification of Cross-sectional Studies - I
Trend Design
Future
Sampling
Population
Cross-sectional studies are carried out on samples taken from the same population at intervals.The assumption is that a representative sampling of the target population has occurred each time. For causal search the trend in one explanatory variable is compared with trends in one or more outcome variables. For example, trends in sale of cigarettes and cancer of the lung, or prohibition of promotion of bottle feeding and prevalence of malnutrition.If the outcome variable changed after the explanatory it provides evidence of time sequence as well as of association.
Risk Factor
Present
Disease Prevalence
Risk Factor
Sampling
Disease Prevalence

10. Modification of Cross-sectional Studies - II
Panel Design
Present
Future
Risk Factor
This is also called Repeat Measure Design. Information is gathered from the same subjects at different time intervals. Sets of data are linked by cases. Changes in one variable helps to identify causal links with changes observed in other variables.
Trend studies only show that over time two variables vary one with the other. By contrast panel design provides more direct evidence that the outcome variable varied after the explanatory variable. Panel design is not entirely immune to spurious association. There may be confounders. However, the main problem is that of attrition.It is very difficult to ensure that all the subjects would continue to participate in the study with full enthusiasm.
Risk Factor
Population
Disease Prevalence
Disease Prevalence
Same Sample
Sample