Persistently low lab values vs persistent low lab values?

I cannot seem to find the best way to express this, both in terms of grammar and "correct sounding" feel to English/American readers (which I am not).

So, this is the scenario: the serum concentration of two peptides, peptide A and peptide B, is measured in a group of patients. The level of these peptides can be either high or low. Patients are tested for both at time zero and after 6 months.
Our interest is on a subgroup of patients who have low levels of peptide A, and not peptide B, at six months. Thus, per our definition, this subgroup of patients includes:

  • those that have a low peptide A (and not peptide B) level at six months, AND
  • had either low peptide A/normal peptide B OR low peptide A/low peptide B at time zero

How would you refer to this group if you wanted to include in one sentence both the persistence of low levels and the fact that this only affects peptide A? I’d like for it to sound natural.

Additional examples for clarity’s sake:
Normal range for pep A is 10-20, anything below 10 is considered low pep A, anything more than 20 is considered high pep A.
Same goes for pep B, identical normal range, identical cut-offs for low and high.

|         | time zero | time zero |  |  |  | at 6 months | at 6 months |
| patient | pep A     | pep B     |  |  |  | pep A       | pep B       |
| 1       | 6         | 11        |  |  |  | 4           | 15          |
| 2       | 6         | 2         |  |  |  | 4           | 4           |
| 3       | 6         | 2         |  |  |  | 4           | 16          |
| 4       | 3         | 11        |  |  |  | 6           | 14          |

Patients 1, 3 and 4 would be included in my group.
Patient 2 would not be included because despite having low pep A both at time zero and at 6 months, pep B is also low both at time 0 and at 6 months.
Note that patient 4 is included in my group despite having an increase in pep A levels: this is because despite the increase he still has low levels (below the normal range).

Would I use persistently decreased or should I use persistently low?

In the latter case, would the following expressions work:

Persistent low levels of peptide A-only;

Persistent A-only hypopeptidemia

(Peptide A is a fictional name, the real name would be similar to hypoalbuminemia and could be styled similarly).


I would phrase this as follows:

Patients who, at 6 months, showed persistently low values of peptide A (and normal peptide B) …

You can further qualify this:

… after initially presenting with low peptide A (and low or normal peptide B) at time zero.

The parenthetical statements are optional if you feel it adds clarity to your statement. But, it also adds complexity.

It all sounds like a mouthful, but being a reader of these types of papers myself, I can say I’d understand your meaning.

Persistently works as an adverb to describe the adjective low which describes the value itself.

Persistent-low values is not preferable because the double adjective is not really a good descriptor for the value. It implies that it’s persistent and low at the same time. It may be, but, you’re not saying the value itself is persistent, but rather the lowness of the value.

In plainer terms: the value is still low (under 10), it’s not still 3 and low. It could be 5 now, which is persistently below the cut off, but not the same that it was originally …..

Above values can be substituted with any appropriate phrase: plasma concentration, levels, etc.

Source : Link , Question Author : user3526613 , Answer Author : David M

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