Q: Can I start a sentence with an abbreviated form?
Say that I have first spelled out a term and then used only its abbreviated form (for example, ‘serum ferritin’ and then ‘sF’). After repeatedly using the abbreviation inline, if I wish to use this to start a sentence, do I use the spelled-out form or the abbreviated form?
The norm is to not begin a sentence with an abbreviation, except if it’s an acronym such as NASA. The rationale for this is that it may look odd right at the beginning of a sentence, especially if it’s not all in uppercase (as in the case of ‘sF’). Additionally, some abbreviations have a period at the end, such as ‘Fig.’ for ‘figure.’ This means that these abbreviations when used at the start of a sentence will have periods right before and after, which could be confusing to read. So, you will need to indeed spell out the term when using it at the beginning of a sentence. Incidentally, if you are asking only about ‘serum ferritin,’ from the few papers we have seen, it seems to be written in full form throughout. Finally, the journal would have its own guidelines that you need to refer to, although most journals also insist on expanding the term at the beginning of a sentence.