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  "path": "/t/french-target-trial-using-obs-data-of-hcq-vs-not-in-sars-cov-2-infection/3206#post_5",
  "publishedAt": "2026-06-06T13:36:46.000Z",
  "site": "https://discourse.datamethods.org",
  "textContent": "Brilliant point that eligibility and time zero are the “natural pair”. Indeed that the natural pair is actually biological state and biological time, with eligibility and time zero serving only as observable proxies.\n\nMinimum requirement (target-trial framework)\n\nT0 = E\n\nEveryone becomes eligible and enters follow-up at the same procedural time.\n\nThis requirement addresses temporal biases arising from misalignment of eligibility and follow-up. It is fundamentally an administrative or methodological requirement rather than a biological one.\n\nStronger requirement\n\nT0 = E = B\n\nwhere (B) is a biologically meaningful state.\n\nUnder this framework, eligibility and follow-up begin at a biologically relevant point rather than at an administrative event. Merely synchronizing on a procedural clock does not guarantee biological coherence. For example, a 48-hour grace period represents approximately two rotations of the Earth. This interval is defined by convention rather than by disease biology.\n\nIn rapidly evolving infections, such delays cannot automatically be regarded as trivial administrative accommodations. In our studies of Ebola viral load and antibody time series, substantial biological evolution occurred over comparable periods. Viral replication, host immune activation, and tissue injury may change markedly during such intervals. A synchronization point defined solely by elapsed clock time therefore risks grouping together patients occupying very different biological states.\n\nStrongest requirement\n\nT0 = E = B(t)\n\nwhere eligibility and follow-up are synchronized not only on the same biological process but also on approximately the same biological time within that process.\n\nUnder this formulation, patients are aligned not merely because they share a diagnosis or biological pathway, but because they occupy comparable positions along the trajectory of that pathway. Two patients with the same infection may differ substantially in biological time despite sharing the same hospital admission date, positive test date, or severity threshold.\n\nAchieving this level of synchronization may require analysis of relational biological time series, including pathogen burden, immune response trajectories, biomarker evolution, physiological adaptation, and other dynamic features that more faithfully represent progression through the disease process than calendar time alone.\n\nThe progression from:\n\nT0 = E.\nto\nT0 = E = B\nto\nT0 = E = B(t)\n\nrepresents a shift from procedural validity, to biological validity, to biological-temporal validity.",
  "title": "French target trial using obs data of HCQ vs not in SARS-CoV-2 infection"
}