Praxis Data Lab · Study Builder

Build your NHANES study with harmonization intelligence.

Combine variables from the indexed Continuous NHANES catalog, choose the cycles you need, and see how Praxis connects source history, methods, cycle boundaries, and cross-code lineage into a study-specific harmonization view.

3variables selected

Praxis identified a method boundary to address

Praxis found a material transition in the selected span and has identified the affected variables so the study can apply the appropriate adjustment.

3 variable assessments

AAXBDMAT

Evidence developinglow confidence

Laboratory

Impermeable Mattress Cover

Source releases: 1
Available cycles: 2005-2006
Dataset: Allergens - Household Dust

No normalized longitudinal change evidence is available for this variable. Absence of events must not be interpreted as proof of cross-cycle equivalence.

Evidence provenance: Praxis automated inference from indexed CDC/NCHS evidence

Remove from study Variable history CDC source

DCDINDEX

Compatible with harmonizationmoderate confidence

Laboratory

Source releases: 3
Available cycles: 1999-2000 · 2001-2002 · 2003-2004
Dataset: Lead - Dust

No blocking method discontinuity is identified inside the selected cycle span, but one or more longitudinal changes require explicit harmonization conditions before pooling.

Evidence provenance: Praxis automated inference from indexed CDC/NCHS evidence

Evidence signals: source-derived · automated-difference

Relevant boundaries: 1999-2000 → 2001-2002 · 2001-2002 → 2003-2004

Praxis harmonization actions

Verify merge grain, companion variables, and component-specific analytic guidance for the new file context.
Review the adjacent codebooks/methods. Keep this boundary as documentation variation unless source evidence confirms a substantive method or instrument change.

Supporting CDC/NCHS evidence

Remove from study Variable history CDC source

GTDDR2MN

Adjustment requiredhigh confidence

Laboratory

Time from glucose challenge & OGTT(min)

Source releases: 5
Available cycles: 2007-2008 · 2009-2010 · 2011-2012 · 2013-2014 · 2015-2016
Dataset: Oral Glucose Tolerance Test

A methodological discontinuity falls inside the selected cycle span. Naive pooling of raw values across the flagged boundary is not recommended unless CDC/NCHS provides a defensible calibration or comparability procedure.

Evidence provenance: Praxis automated inference from indexed CDC/NCHS evidence

Evidence signals: source-derived · automated-difference · source-stated

Relevant boundaries: 2007-2008 → 2009-2010 · 2009-2010 → 2011-2012 · 2011-2012 → 2013-2014 · 2013-2014 → 2015-2016

Praxis harmonization actions

Verify merge grain, companion variables, and component-specific analytic guidance for the new file context.
Review the adjacent codebooks/methods. Keep this boundary as documentation variation unless source evidence confirms a substantive method or instrument change.
Select the weight appropriate to each cycle and subsample; when pooling cycles, construct the combined weight according to NHANES guidance rather than reusing a single-cycle weight unchanged.
Apply CDC/NCHS comparability or calibration guidance where available. If equivalence is not established, preserve separate method periods or perform sensitivity analyses rather than naively pooling raw values.

Supporting CDC/NCHS evidence

Remove from study Variable history CDC source