By writing a working abstract at an early stage, you will provide yourself with a framework for the rest of the article. It will guide you in deciding what to include and what to omit, thus sparing you tedious rewriting. Then, when you have completed the paper, you can return to the working abstract and recast it in its final form.

Let us consider here what to include. In both types of abstract, the conventional (unstructured) and the formally structured, the same four basic sections are required: Background (including the purpose of the study), Methods, Results, and Conclusions

The conventional abstract

In the conventional abstract, the four basic components are not identified with explicit headings, which may explain why some authors miss out vital parts. In the worst instance, the abstract contains neither background nor conclusion. Many abstracts written in the conventional manner are uninformative and cause editors much unnecessary editorial trouble. The following abstract, quoted from an article in Contraception, commences directly with the method:

Most journals reporting laboratory studies use the conventional abstract, and it is usually applied to Case Reports and Briel Communications. Clinical journals, however, often require a structured abstract for full-length papers.

The structured abstract

The structured abstract differs from the conventional abstract by having a heading for each section. Here is such an abstract of the classic The chromosome number of man by Tjio and Levan (1956).