Handling samples with unknown sample collection time [PK / PD]

posted by lechia – C of U, 2017-05-18 23:47  – Posting: # 17370
Views: 2,216

Hi all,

I'm curious about your approach to handling samples that were collected, but the time of collection is uncertain. Let me explain by some examples:

Example 1: Time of one blood draw was not recorded at all. Only scheduled time is known.

Example 2:

Scheduled timepoint X: 20:05
Recorded time (time recorded by the person collecting the blood): 20:05

Scheduled timepoint X+1: 24:05
Recorded time: 20:07

Scheduled timepoint X+2: 06:05
Recorded time: 06:05

Example 3:

Scheduled and recorded timepoint X: 10:12

Scheduled timepoint X+1: 11:12
Recorded timepoint X+1: 11:21

Scheduled and recorded timepoint X+2: 12:12

In all cases, the person collecting the blood did not record that the deviation was out of window where it had to be if we take the time as written. All other evidence points to the fact that most likely the wrong time was recorded, eg. in example 3, this person would have been busy with another subject at 11:20 and 11:22, so it was virtually impossible for her to have actually collected this blood at 11:21. Most likely 12 was incorrectly written as 21.

I believe that in all cases, the most stringent approach should be taken and the sample should be considered as if it was missing. Seems like the easiest approach to keep agencies happy that no manipulation has taken place. Do you agree or do you then use the nominal time or do you keep the time as recorded even if it's again hard to fathom that a person would collect blood draws scheduled so far away only two minutes apart (example 2)?

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