Tense indicates the time relation of a verb: present (I am), past (I was), future (I will be), present perfect (I have been), past perfect (I had been), and future perfect (I will have been). It is important to choose the verb that expresses the time that is intended. It is equally important to maintain consistency of tense.
The present tense is used to express a general truth, a statement of fact, or something continuingly true.
For this reason, the present tense is often used to refer to recently published work, indicating that it is still valid.
Kilgallen’s assay results demonstrate the highest recorded sensitivity and specificity to date.
The present perfect tense illustrates actions completed in the past but connected with the present2 or those still ongoing. It may be used to refer to a report published in the recent past that continues to have importance.
Kaplan and Rose have described this phenomenon.
The past tense refers to a completed action. In a biomedical article the past tense is usually used to refer to the methods and results of the study being described:
We measured each patient’s blood pressure.
Group 1 had a seropositivity rate of 50%.
The past tense is also used to refer to an article published months or years ago that is now primarily of historical value. Frequently a date will be used in such a reference.4
In their 1985 article, Northrup and Miller reported a high rate of mortality among children younger than 5 years.
In general, tense must be used consistently:
There were no adverse events reported in the control group, but there are 3 in the intervention group.
There were no adverse events reported in the control group, but there were 3 in the intervention group.
However, tense may vary within a single sentence, as dictated by context and judgment.
We determined which medications are used most frequently by this population.
Alternatively, the past tense and the present tense may be used in the same sentence to place 2 things in temporal context:
Although the previous report demonstrated a significant response, the follow-up study does not.
Even when tenses are mixed, however, consistency is still the rule:
I found it difficult to accept Dr Smith’s contention in chapter 3 that the new agonist has superior pharmacokinetics and was therefore more widely used.
I found it difficult to accept Dr Smith’s contention in chapter 3 that the new agonist has superior pharmacokinetics and is therefore more widely used.