Comparison
Read Your Scan Editorial Team·Last updated
Written from published radiology references and reviewed for plain language. Not written or signed by a physician, and not a diagnosis. How we write these pages →
In plain language
Which earlier scans the radiologist had in front of them while reading this one. "No comparison available" or "none" means this is the first look, so nothing could be measured against a previous state — which is why a first scan often reads more cautiously than a follow-up.
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Where you'll see this
Near the top of the report, just after the technique.
Your report may word it “Comparison study”, “Prior studies” or “Priors”. These mean the same thing.
Questions worth asking your doctor
- Which part of this report is the conclusion I should focus on?
- Was the question my doctor asked actually answered by this scan?
- Is there an earlier report or addendum I should be reading alongside this one?
How often does this turn up?
The comparison line states which previous imaging the radiologist looked at alongside the current study, or records that none was available. It appears on most reports and is far more important than its single line suggests, because in radiology change over time is often more informative than any single image.
Does it mean something is wrong?
The phrase to notice is no prior imaging available for comparison. That is not a criticism — it is a statement that the radiologist had to judge everything on today’s pictures alone, without the single most powerful piece of context there is. Something unchanged over years is usually benign; the identical appearance seen for the first time may need working out. So a report with no comparison is more likely to recommend follow-up, not because anything is suspicious but because time has not yet been allowed to answer the question.
What to do with it
If you have had imaging elsewhere — a different hospital, another country, years ago — telling the department is genuinely useful and can spare you a follow-up scan entirely. Where a comparison was available and the report says something is stable or unchanged, that is one of the most reassuring sentences a report can contain, and it deserves more weight than the description of the finding itself.
Frequently asked questions
- Why does the report say no comparison available?
- Because no earlier imaging of that area was accessible to the radiologist. It is a statement about what they had to work with, not about anything found — and it is a common reason for a follow-up scan to be recommended.
- Should I tell them about scans done elsewhere?
- Yes, and it is worth doing before the appointment. Older images can settle a question immediately, and can spare a follow-up scan arranged only to demonstrate stability that a previous study would already have shown.
- Why is comparison so important?
- Because behaviour over time distinguishes benign from otherwise more reliably than appearance at one moment. Something identical to how it looked five years ago rarely needs pursuing; the same thing appearing for the first time may.
Parts of a report
Where this word comes up
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