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AF labels in SHHS

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jbehar +0 points · 2 months ago

Dear Mark/Stephanie,

Regarding the AF labels provided in the SHHS variables. There seems to be three options available as part of the SHHS:

1/ AFIB: atrial fibrillation or flutter Visit 1 and visit 2 Minnesota (MN) code 8-3-1 or 8-3-2. Data derived from standard resting 12-lead electrocardiogram (ECG) with the participant supine. Records were interpreted and Minnesota (MN) codes were provided by clinical cardiologist

2/ AFIB Prevalent At the first visit Variable created as part of the analysis for Tung et al. 2017 (PMID: 28668820). Prevalent AF was defined by any of the following: a positive response to the question 'Has a doctor ever told you that you have or had atrial fibrillation'; AF identified on resting 12-lead ECG at the baseline SHHS exam; or if the parent study identified AF documented in the medical record before the SHHS baseline exam.

3/ AFIB incident After SHHS visit 1 Variable created as part of the analysis for Tung et al. 2017 (PMID: 28668820). Incident AF was considered present if AF was identified on a 12-lead ECG obtained at the second SHHS exam or was adjudicated by the parent cohorts at any time between the baseline PSG and the final follow-up date for AF ascertainment of June 30, 2006.

For variable 2 and 3 the paper from Tung et al. is referenced. For the first variable there is no reference. In addition, there are important differences in the number of cases between the variables. For example in AFIB there are 80 individuals classified as AF during the second visit whereas in AFIBincident there are 332 cases of AF at visit 2.

Do you have some more information/comments/explanation on how to understand the difference between these variables and which one is the most accurate diagnosis of AF during visit 1 and during visit 2?

Many thanks, Joachim

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mrueschman +0 points · 2 months ago

Note that #2 and #3 take into account the "afib" variable as part of their derivations. Then for the Tung analysis she obtained additional parent cohort data that extended from the end of SHHS Visit 2 up until 2006.

These AF variables are difficult to interpret, in my opinion. For #1 you need to consider the ecgdate variable, given that the ECGs of interest were often not completed at the SHHS exam. The ECG data are "B Variables".

Furthermore, as you'll see from the missingness, not all cohorts had ECG data to share and/or may not have contributed supplemental data for the Tung AF analysis.

Directly to your question, I think the "afib" (#1) variable is the best representation of the presence of AF nearest to the two SHHS exams.

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jbehar +0 points · 2 months ago

Thanks Mark, We will dig more into this given your input. Hopefully, that will be enough Best, Joachim

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jbehar +0 points · about 2 months ago

Hi Mark, A further question on this topic. The "afib" label is meant to represent persistent AF or atrial AFL as per the Minnesota (MN) code 8-3-1 or 8-3-2. I believe these were extracted from the EMR system and are part of the patient history. My question is, do we know if these patients were treated (and if yes how) for AF/AFL? In other words, I am looking to understand how much these variables are representative of the AF/AFL status at SHHS1. Thank you, Joachim

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mrueschman +0 points · about 2 months ago

Here's some more information on the ECG data present in the SHHS dataset:

Baseline ECGs were performed by the parent cohorts prior to the PSG. All Field Sites performed a standard resting 12-lead ECG with the participant supine. Ten seconds of data were acquired simultaneously from each lead (I, II, III, aVR, aVL, aVF, V1-V6) to a Marquette MAC PC or MAC II system. At each site, a paper copy of the ECG is produced and filed. Minnesota coding of the ECG data is performed on all participants in ARIC, CHS, and SHS. Minnesota coding may be performed for other sites as well. Currently, NYCC ECG data were interpreted by a clinical cardiologist, and FHS ECG data were interpreted by the clinic physician. Minnesota codes provided by the Field Sites were then used to derive the 34 variables in the ECG dataset.

My guess is that the parent cohorts tracked additional details (e.g. ongoing presence, treatment) about each participant's AF, though these details did not trickle down into the SHHS datasets since these were secondary to the original outcomes of SHHS.

PS. It's Mike, not Mark!

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jbehar +0 points · about 2 months ago

Hi Mike (my apology for the mistake), Thanks for the precision. Do you know who is the contact person(s) from the original studies that I can ask for recovering this information? It would be very valuable to have for our current work this is a variable we can add to SHHS. Cheers, Joachim

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mrueschman +0 points · about 2 months ago

Here are the parent cohort sites where I would start:

The NSRR does not have ongoing relationships directly with these cohorts. I expect each one has different policies and procedures regarding access to supplemental data.

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jbehar +0 points · about 2 months ago

Thanks Mike, I will try my luck, Joachim