PRISMA 2020 flow diagrams that survive Word

A PRISMA diagram drawn from separate shapes in Word can move apart when the text around it changes. This guide shows why, holds the diagram together, and brings it to the width, resolution and typeface a journal or a thesis asks for.

It ends with a checklist to go through before you submit, and a caption to adapt.

Before you start

• Your numbers, counted and checked. The PRISMA 2020 flow diagram: counting every box goes through them box by box.
• The official template that fits your review (see the next section).
• Your journal’s instructions for figures, or your thesis regulations. They set the width, resolution, file type and typeface, and they have the last word over anything here.

Start from the official template

The PRISMA 2020 flow diagram page offers four Word templates: for a new or an updated review, each with databases and registers only or with other sources as well. They are the originals, so take yours from there. They are published under CC BY 4.0, and you do not need permission to use one in your review (Rethlefsen and Page 2022). The same page links a Shiny app that draws the diagram from numbers you type in (Haddaway et al. 2022).

Fill in the numbers and your reasons, and keep every box label word for word; the guide linked above lists them all.

Keep the shapes together while you edit

In Word, every picture or shape that is not in line with the text has an anchor. Microsoft explains that the anchor “indicates the paragraph with which the object is associated”, and with “Move with text” set, the object moves when that paragraph moves. A diagram made of many loose shapes has many anchors, so an edit above it can move some boxes and not others.

Two things hold the shapes together while you work:

• Group them. Select all the shapes, then choose “Group” on the “Shape Format” tab, “so that all of the shapes will be treated like a single object” (Microsoft Support).
• Or draw inside a drawing canvas (“Insert” › “Shapes” › “New Drawing Canvas”). Microsoft suggests one “as an organizational aid when working with several drawing objects, or if you want to add connectors between shapes”.

Put it in line with the text

When the diagram is finished, set the group or canvas to “In Line with Text” (“Wrap Text” on the “Shape Format” tab), in a paragraph of its own. Microsoft describes inline objects as “treated like any text character”: they “automatically move with the surrounding text”, and anchors “do not appear for inline pictures”. A diagram that behaves like one character cannot come apart.

A picture file behaves the same way. Insert it, set it to “In Line with Text”, and put the caption in the paragraph below it (see “Writing it up”).

Send the journal a file of its own

A journal may want the figure as a separate file. Elsevier, for example, prefers figures uploaded apart from the manuscript. It lists EPS, PDF, TIFF and JPEG, and accepts Office files too: its FAQ says to “submit MS Office documents directly”, so a filled-in Word template can go as it is. The same FAQ says its submission systems are still being updated to take PNG files. Check your own journal’s list before you choose.

Size it for the page

Make the figure at the width it will print, so that its type prints at the size you set. Elsevier’s widths are 90 mm for a single column, 140 mm for one and a half columns and 190 mm for the full width. On an A4 page with 2.54 cm margins, the text is 159 mm wide.

For type, Elsevier’s rule of thumb is 7 pt for normal text at the printed size, and no smaller than 6 pt for subscripts and superscripts. It names Arial (or Helvetica), Courier, Symbol and Times (or Times New Roman), and says that other fonts may be replaced, which “may lead to problems such as missing symbols or overlapping type”. For lines it recommends 0.25 pt, and 0.1 pt at the very least. If the figure may be printed in black and white, check that its box colours do not turn into similar greys.

Choose the resolution

A picture file (PNG, TIFF, JPEG) has a fixed number of pixels, so how sharp it prints depends on its width. Elsevier puts it as “Pixels = Resolution (DPI) × Print size (in inches)”. It asks for 300 dpi for halftones, 500 dpi for combination art and 1,000 dpi for line art, which it describes as “purely black and white with no tints or gradations”. If you are not sure which fits your diagram, use the higher number, or send a vector file.

For any other width, pixels = mm ÷ 25.4 × dpi, rounded. In a spreadsheet:

With 90 in A2 and 300 in B2, C2 gives 1,063.

A vector file (EPS or PDF) has no pixels to count: Elsevier calls pure vector images “resolution independent”. Adding pixels to a small picture afterwards does not help; in Elsevier’s words, “increasing the image resolution will never improve the quality of the image”.

Stop Word shrinking the picture

Word can compress the pictures in a document. Microsoft gives the default picture resolution in Microsoft 365 as 220 ppi, below the 300 dpi Elsevier asks for halftones, and notes that turning compression off “improves picture quality, but uncompressed pictures could result in very large file sizes”. In Word for Windows, go to “File” › “Options” › “Advanced”, and under “Image Size and Quality”:

• select “Do not compress images in file”;
• set “Default resolution” to “High fidelity”, which keeps pictures from being compressed “unless they exceed the size of the document canvas”.

Both apply to the document named in the list beside “Image Size and Quality”, unless you choose “All New Documents”. On a Mac, “Default resolution” is under “Word” › “Preferences” › “Edit”.

Word cannot show you a picture’s resolution. Elsevier’s FAQ says that “it is not possible to check image resolutions in MS Word directly”, so check the file before it goes in.

Check the file that arrived

Whatever made the picture, whether the Shiny app, a drawing program or a screening tool, check it before you insert it. Find its width in pixels, and divide by the width it will print at, in inches (millimetres ÷ 25.4). A picture 2,000 pixels wide, printed at 190 mm, comes to 2,000 ÷ 7.48 = 267 dpi: short of 300. Make it again at the size you need, print it narrower, or use a vector file.

Check your work

• The box labels match the template word for word.
• The numbers match your tally sheet, and every sum holds.
• The diagram is one object, in line with the text, in a paragraph of its own; or it is a file of its own for the journal.
• It is at its final width, and its smallest type is at or above your journal’s minimum at that width.
• A picture file has the pixels its width and resolution need (Table 1), or the figure is a vector file.
• Word’s picture compression is off for this document.
• The typeface is on your journal’s list, and the colours stay distinct in black and white.
• The caption is text, and the template is credited.

Writing it up

Put the caption in the text, not in the image. In a thesis, use Word’s own captions (“References” › “Insert Caption”): Word inserts the number as a field, and can update every caption number at once. For a journal, Elsevier asks for captions in the submission system’s “Figure Caption” item, or listed at the end of the manuscript.

A caption to adapt:

Figure [n]. PRISMA 2020 flow diagram of the search and selection of studies. Template from Page MJ, McKenzie JE, Bossuyt PM, et al. BMJ 2021;372:n71 (CC BY 4.0).

The template’s own credit, “Source: Page MJ, et al. BMJ 2021;372:n71. doi: 10.1136/bmj.n71.”, can stay under the diagram instead, with its licence line. The licence lets you give the credit “in any reasonable manner based on the medium” (CC BY 4.0, section 3(a)(2)). If you changed the template beyond filling it in, say what you changed (section 3(a)(1)(B)).

Reading on

• The PRISMA 2020 flow diagram: counting every box
• The PRISMA 2020 flow diagram page, with the four templates
• Elsevier: artwork sizing
• Microsoft Support: wrap text and move pictures in Word