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Decision-ready map
• Program risk: rigid thresholds can misclassify differently by sex/life stage
• Procure devices with sex-stratified evidence and model/firmware transparency
• Train for technique + mismatch escalation (symptoms override numbers)
• Include pregnancy/anemia pathways in SOPs and referral criteria
• Audit outcomes by sex (and life stage where ethical/lawful)
(1) What it is
Optical tools scale quickly in community programs (wearables, spectroscopy, NIRS). Sex-linked differences in Hb, perfusion, and skin scattering can shift signals and make rigid thresholds unsafe—especially in pregnancy/anemia-heavy contexts. Validate that procurement, SOPs, and referral pathways prevent sex-linked misclassification when confirmatory testing is limited.
(2) Who it helps
Organizations that buy/distribute devices, design screening/triage pathways, train staff, or publish guidance—especially when decisions are threshold-driven.
(3) What evidence exists
Sex-dependent PPG features (Dehghanojamahalleh & Kaya 2019). Population DRS inversions show sex-associated absorption/scattering (Jonasson et al. 2023; Hung et al. 2015). Microcirculation differences affect amplitude/quality (Samils et al. 2023). Time-resolved NIRS shows sex differences in baseline oxygenated hemoglobin (Asahara & Matsukawa 2023). Skin fluorescence differs by sex (Morvová et al. 2018). WHO Hb guidance differs by sex/pregnancy (WHO 2024).
(4) Translation barriers
Commodity procurement without model/firmware transparency; training that overemphasizes numbers; field artifacts (cold, motion, dehydration); limited subgroup data capture; ethical constraints around collecting sensitive data.
(5) Equity/safety checks
Require sex-stratified evidence and device transparency; avoid single-cutoff rules; train symptom-first mismatch escalation; handle sex/pregnancy information with consent and privacy safeguards; audit outcomes by sex where ethical/lawful.
(6) Decision questions
• Are referral decisions threshold-driven and sensitive to subgroup shifts?
• Do vendors disclose model/firmware and provide sex-stratified evidence?
• Are pregnancy/anemia pathways explicit in SOPs?
• Are staff trained on technique/quality flags/mismatch escalation?
• Is there incident reporting and equity auditing?
(7) Practical next steps
1) Update procurement specs (transparency, sex-stratified evidence, change control).
2) Publish a one-page SOP (technique, quality checks, mismatch rule, referral).
3) Train staff with pregnancy/anemia scenarios.
4) Implement incident reporting + quarterly review stratified by sex.
5) Communicate benefits, limits, and safeguards transparently.
(8) References
Dehghanojamahalleh S, Kaya M. Sex-Related Differences in Photoplethysmography Signals Measured From Finger and Toe. IEEE J Transl Eng Health Med. 2019;7:1900607.
https://doi.org/10.1109/JTEHM.2019.2938506
Charlton PH, Pilt K, Kyriacou PA. Establishing best practices in photoplethysmography signal acquisition and processing. Physiol Meas. 2022;43(5):050301.
https://doi.org/10.1088/1361-6579/ac6cc4
Jonasson H, Fredriksson I, Bergstrand S, et al. Absorption and reduced scattering coefficients in epidermis and dermis from a Swedish cohort study. J Biomed Opt. 2023;28(11):115001.
https://doi.org/10.1117/1.JBO.28.11.115001
Samils L, Henricson J, Strömberg T, Fredriksson I, Iredahl F. Workload and sex effects in comprehensive assessment of cutaneous microcirculation. Microvasc Res. 2023;148:104547.
https://doi.org/10.1016/j.mvr.2023.104547
Asahara R, Matsukawa K. Prefrontal oxygenation is quantified with time-resolved NIRS: effect of sex on baseline oxygenation and response during exercise. Am J Physiol Regul Integr Comp Physiol. 2023;325:R31–R44.
https://doi.org/10.1152/ajpregu.00048.2023
Morvová M Jr, Jeczko P, Šikurová L. Gender differences in the fluorescence of human skin in young healthy adults. Skin Res Technol. 2018;24(4):599–605.
https://doi.org/10.1111/srt.12471
Hung C-H, Chou T-C, Hsu C-K, Tseng S-H. Broadband absorption and reduced scattering spectra of in-vivo skin using δ-P1 approximation. Biomed Opt Express. 2015;6(2):443–456.
https://doi.org/10.1364/BOE.6.000443
Staritzbichler R, Hunold P, Estrela-Lopis I, et al. Raman spectroscopy on blood serum samples of patients with end-stage liver disease. PLoS One. 2021;16(9):e0256045.
https://doi.org/10.1371/journal.pone.0256045
WHO. Guideline on haemoglobin cutoffs to define anaemia in individuals and populations. 2024.
https://www.who.int/publications/i/item/9789240088542
NIH Office of Research on Women’s Health. Sex as a Biological Variable (SABV).
https://orwh.od.nih.gov/sex-as-biological-variable
FDA. Evaluation of Sex-Specific Data in Medical Device Clinical Studies (final guidance). March 2025.
https://www.fda.gov/regulatory-information/search-fda-guidance-documents/evaluation-sex-specific-data-medical-device-clinical-studies-guidance-industry-and-food-and-drug