Writing an abstract
The abstract is likely the first thing your readers will look at in order to form an opinion of whether or not your text is of interest to them. An abstract is a brief summary of a longer text, such as a thesis, a research article, or a conference paper. It is placed at the very beginning of an academic text, and should provide an overview of the contents of the full text.
Format and structure
The length of an abstract can vary, but it is often between 200-300 words long. The brevity of an abstract means that you must consider what information to include, and what information to leave out. Strive to write short, concise, and clear sentences. At the same time, the abstract must also function as a coherent text on its own.
The abstract follows the structure of conventional academic texts but in a more compressed format. Some or all headings of an academic text such as introduction, aim, method, results, and conclusion are often included in the abstract. The different sections can be explicitly stated as headings in bold font (see the example abstract further down). Certain abstracts may also contain a separate discussion heading, but that is less common. Sometimes there are no explicitly stated headings, but the structure of the abstract always reflects each section found in a conventional academic text.
The results and the conclusion are the most important sections of your abstract. These sections are what your readers are the most interested in. Therefore, they should also take up the most space in your abstract. In contrast, the fewest number of words should be devoted to the background. A common mistake is to include too much background information. The background part of a standard-length abstract should comprise, at most, two to three sentences.
Below is an example abstract with comments included that discuss various sections. Note how key words and concepts from the aim are reflected throughout the rest of the abstract (underlined in the text):
Sample abstract with comments
| Example | Comment |
|---|---|
| Background Early and accurate prediction of hospital surgical-unit occupancy is critical for improving scheduling, staffing and resource planning. Previous studies on occupancy prediction have focused primarily on adult healthcare settings, we sought to develop occupancy prediction models specifically tailored to the needs and characteristics of paediatric surgical settings. | Devote the least amount of space to summarising the background. A sentence or two will usually suffice in a standard length abstract.
In the background section of this abstract, the first sentence explains the relevance of the study. The second sentence presents previous research, followed by the aim of the study. This means that the structure of the very brief background information in the abstract reflects the funnel shape of the background section in the article proper. You can read more about introductions and the funnel structure here. |
| Materials and methods We conducted a single-centre retrospective cohort study at a surgical unit in a tertiary-care paediatric hospital in Boston, Massachusetts, USA. We developed a hierarchical modelling framework for predicting next-day census using multiple types of data—from bottom-up patient-specific orders and procedures to top-down temporal variables and departmental admission statistics. |
Description which is detailed enough that the reader may fully understand the method used, but not nearly as detailed as the actual method section in the paper or essay itself. The exact contents and detail of this part of the abstract can vary greatly depending on field, subject, and publication. Therefore, it may be a good idea to look at a few relevant examples of abstracts from your field which describe a similar methodology to yours. Note what is included or omitted in those example abstracts. |
| Results The model predicted upcoming admissions and discharges with a median error of 17%–21% (2–3 patients per day), and next-day census with a median error of 7% (n=3). The primary factors driving these predictions included day of week and scheduled surgeries, as well as procedure duration, procedure type and days since admission. We found that paediatric surgical procedure duration was highly predictive of postoperative length of stay. | This is often the longest part of an abstract as key findings are presented here. Consider starting with the most important aspect of the results to ensure the reader takes that with them from the text. |
| Conclusion Our hierarchical modelling framework provides an overview of the factors driving capacity issues in the paediatric surgical unit, highlighting the importance of both top-down temporal features (eg, day of week) as well as bottom-up electronic health records (EHR)derived features (eg, orders for patient) for predicting next-day census. In the practice, this framework can be implemented stepwise, from top to bottom, making it easier to adopt. Modelling frameworks combining top-down and bottom-up features can provide accurate predictions of next-day census in a paediatric surgical setting. |
Results and conclusion together normally take up most of the space in the abstract. In the conclusion, use the same keywords as in your aim, so that the connection between aim and conclusion is as clear as possible. In this example, these keywords are ”paediatric surgical setting” and "occupancy prediction model". They recur in different forms throughout the abstract, and we have underlined them in the abstract text. This final part of the abstract should present the take-home message to your reader. Be specific, and avoid sweeping or general claims. |
Source (slightly adapted for pedagogical purposes):
Barak Corren Y, Merrill J, Wilkinson R, et al. Predicting surgical department occupancy and patient length of stay in a paediatric hospital setting using machine learning: a pilot study. BMJ Health & Care Informatics 2022;29:e100498. doi: 10.1136/bmjhci-2021-100498
The whats and whys of graphical abstracts
The ability to visually summarise the key findings of an article is becoming increasingly important. By creating a graphical abstract for your paper, you can draw attention to your written abstract and full text.
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