How Trévor calculates

Every figure, label or piece of advice from Trévor comes from a calculation described here: what it reads, its steps as a flowchart, its values and its limits.

Crisis, form and advice

• Crisis risk alerts and notification limit : If you turned it on, Trévor writes to you every morning around 8 a.m. when your crisis risk reaches 70% on fresh measurements. An optional soft alert exists from 40%. It never sends more than one alert message per day, and it holds the message during quiet hours.
• Learning the personal model and the cohort model : Each night, Trévor can train a logistic regression model on your own days, then a model shared by everyone being followed. The starting weights come from a clinical prior, and training moves them away only if your data justify it. At calculation time, the models that have proven themselves are blended with the prior.
• Daily readiness (recovery) : The daily readiness is a recovery marker out of 100, in the manner of an Oura score. Trévor shows your device's own score as is when one exists. Otherwise it computes its own from your sleep, heart rate variability (HRV) and resting heart rate, compared with your normal.
• Baselines and deviations from your normal : Trévor compares each measurement from your watch or ring with what is usual for you, rather than with a general norm. It computes a median and a median absolute deviation (MAD) over your previous days, then turns today's gap into a robust z-score and a 3-day trend. These gaps are the raw material of the crisis risk, the dip-in-form risk and the daily readiness.
• What should I do now? : When your crisis risk rises, your form is medium or low, or pain starts, Trévor suggests 3 to 5 concrete gestures. It always starts with the safety instruction if it sees an emergency sign, then puts forward the gestures that already helped you, the general markers, and finally what other people observe if there are enough of them. These are general self-care gestures, never a medication dose.
• Risk of a dip in form : The risk of a dip in form is a second score, softer and more frequent than the crisis risk. It estimates the probability of a drop in your daily functioning (sleep, energy, pain) within 48 hours. It is meant to help you act early, for example with rest, hydration and a calmer pace, before a possible crisis.
• Watch signals and temperature and heart sources : Trévor reads three families of signals from your watch, ring or files. The factual signals are simple markers (SpO2 below 92%, resting HR 10 bpm higher, short sleep, etc.) shown with their date. Three temperature and heart features enter the crisis risk with modest weights, and the signals module compares temperature and heart with your baseline for its own screens.
• Vasoconstriction trend (experimental) : This indicative index spots skin that cools more than usual during the night, a possible sign of vasoconstriction. It compares your skin temperature, resting heart rate, HRV, oxygen and breathing with your previous 14 days. It stays silent when the measurement is fragile, and it is only computed if you gave your consent.

Night, oxygen and measurements

• Sensor and algorithm bias: what Trévor says and the measures offered : Trévor explains that oximeters, watches, rings and phone cameras can show oxygen higher than reality on dark skin, and that its own calculations inherit this bias. It offers five practical measures. This text is displayed and is not a calculation.
• Weather and air quality at your home location : Each day Trévor fetches the weather and air quality where you live and keeps a daily summary, to set it beside how you are doing. It invents nothing: with no location or no service response, the series stays empty.
• Daily watch measurements: steps, pulse, HRV, temperature, stress, and detected signals : Trévor stores your watch or ring measurements as one value per day, drops impossible values, fills in the temperature deviation when the device gives only the temperature, then compares your last 7 days with the 30 days before. It also lists factual signals (low oxygen, high pulse, low HRV, temperature, breathing, short nights). This is not a validated medical device.
• Fifteen days of "moments": summary of your hard moments and the environment : If you turn it on, for fifteen days Trévor asks twice a day how you feel right now (good, medium, not good). At the end it compares hard days with other days on the environment and writes at most two conditions that differ, without speaking of cause.
• My night: your usual range, lower nights, time below 90 percent and alerts : Trévor compares each night's average oxygen to your own usual range from the previous 30 nights and flags nights that are clearly lower. It also reports time below 90 percent, a run of low nights and a very low measured oxygen, in which case safety comes first. This is not a diagnosis.
• Night oxygen: average, lowest point, time below threshold, desaturation index : When your watch or ring sends a series of oxygen readings during the night, Trévor boils it down to a few numbers: average, lowest point, share of the night below 92, 90 and 88 percent, and drops per hour. These numbers feed the "My night" screen and your usual range. This is not a validated medical device.
• Night quality, ignored nights and source choice : Trévor rates each measured night "good", "medium" or "low" based on measured time, coverage and movement. A "low" night stays visible but is left out of every calculation (your usual range, lower nights, curves). When several sources describe the same night, Trévor keeps the best one.
• Manual entry: night oxygen, fingertip oximeter, how you slept and bedtime : When your watch does not send the night's oxygen, you can type it yourself, along with a fingertip oximeter value, how you slept and an approximate bedtime. Trévor stores these entries as measurements without correcting them.
• Night sleep: duration, efficiency, awakenings : Trévor takes what your device reports about your night (time asleep, time in bed, awakenings, stages) and computes only what can be computed without inventing anything, such as sleep efficiency. It then compares your night to your own usual range to spot a fragmented night.
• Oxygen estimate from the phone camera (experimental) : The phone has you rest your finger on the lens and flash, measures how the light pulses, and sends Trévor a ratio R, the signal quality and the pulse. Trévor converts R into a SpO2 estimate with a range, wider until you calibrate with a reference oximeter. This is experimental and not a validated medical device.
• Watch measurement quality: good, medium or insufficient : Trévor counts over 14 days how many days have enough useful measurements, and from that decides whether your watch gives "good", "medium" or "insufficient" measurements. This label is used to silence a fragile conclusion and to show reliability on the wrist and in the bot.
• Aligned series of the "dashboard of your life" : Trévor puts on the same day axis what you experience (pain, mood, form, fatigue, crisis days), your body (watch, nights, lab results), the environment, your care and event markers. It computes no averages and no interpolation: a day without a measurement stays empty.
• The low oxygen threshold (92 percent) and nearby thresholds: where they apply and how to set them : Trévor uses several oxygen thresholds in different places: 92 percent for a single value, 90 and 88 percent for time spent at night, and 88 percent for emergencies. The 92 percent cannot be changed; you can only set your own usual range, which changes when an alert is sent.
• Usual range of each measurement and value alerts : Trévor reads your latest value against two references: the general adult norm and your usual range, learned from your own values or set by you or your clinician. Depending on whether the value is outside one, both or neither, it shows "alert", "watch", "usual for you" or "nothing to report". This is not a diagnosis.

Blood and hemolysis

• Entry and conversion of lab results : When you type a lab value, or when Trevor reads one in a document, it converts it to the unit of its catalog, checks that it is plausible and not already in the record. These rules serve hemolysis, iron, fetal hemoglobin and creatinine. The original unit is kept next to the converted value.
• Hemolysis assessment: six markers against your own baseline : Trevor compares your latest value of each marker (total and indirect bilirubin, LDH, reticulocytes, haptoglobin, hemoglobin) with the median of your earlier values. It counts how many recent markers move in the direction of hemolysis and derives a level: stable, to watch, or suggests a hemolysis flare. It describes your data and makes no diagnosis.
• HemoSnap: hemoglobin estimated from a fingertip photo : HemoSnap estimates your hemoglobin from three photos of a fingertip placed over the camera lens and flash. A number appears only after calibration on one of your lab values. It is an experimental feature with no clinical validation and does not replace a blood test.
• Scleral yellow: index and estimated bilirubin : Trevor measures the yellow of the white of your eye from a photo and derives an index. After several photo and blood test pairs, it converts the index into an estimated bilirubin with an interval. Without calibration, it only says whether you are more yellow, the same, or less yellow than usual.
• Reading a lab PDF : Trevor reads the words and their positions in a lab PDF that contains text, finds the hemolysis markers and attaches each value to its sampling date. Nothing is invented: a value is kept only if it is aligned under a date. You review the result before anything is saved.
• Hemoglobin response to transfusions : Trevor compares your hemoglobin before and after each transfusion to estimate what one unit gives you, how long the gain lasts, and whether exchanges respect the dose and interval of their protocol. It describes your data and recommends no dose.
• Iron follow-up: ferritin, MRI and ejection fraction : Trevor records the iron measurements your care team gives you (ferritin, heart and liver T2*, liver iron, ejection fraction), plots them and reads them against reference points from the Thalassaemia International Federation. Each entry resets the reminder for the annual exam. It gives no treatment instruction.
• Symptoms after a transfusion: alert level : You tick the symptoms you have felt since a transfusion. The server gives the declaration the level of the most serious symptom ticked: warning sign, to report, or noted. It then tells you whom to call, and flags a possible delayed reaction if the sign and timing fit.
• Transfusion history, interval and program : Trevor finds your last transfusion from the several places where you may have noted it, counts the days elapsed, computes the mean interval between transfusions and, if you have a regular program, says whether you are late or on time. It also records the number of units and the length of each session.

Treatments and questionnaires

• Personal associations : Trévor looks in your own data for cautious links between what you do or what surrounds you (sleep, weather, treatments, actions) and your pain, mood, form, fatigue or crises. A displayed link is not a cause.
• Personalized screening calendar : Trévor reads a rules table (age, genotype, treatment) to tell you which monitoring exams recur at which pace, and when the next one is due based on the last date you enter. It organizes your follow-up, interprets no result and does not replace your care team.
• Stress load and resources ("balance") : Trévor adds load points (stress, mood, PHQ-9, GAD-7, life events) and resource points (good things noted, supports, mood, calm) over 30 days and shows them side by side as two percentages. It is a project index with no clinical validation.
• Short screeners: post-traumatic stress, ADHD, autism : Trévor counts your answers to three short questionnaires (PC-PTSD-5, ASRS v1.1 part A, AQ-10) and says whether the screen is "positive", which means a professional opinion is suggested. This is not a diagnosis or a validated medical device: the result points you toward a professional.
• Depression and anxiety: PHQ-9, GAD-7 and Edinburgh scale : Trévor adds up your answers to the PHQ-9 (mood), GAD-7 (anxiety) and, during the postpartum period, the Edinburgh scale (EPDS). It gives a score, a level and advice, and always handles first any answer that suggests thoughts of self-harm. This is not a diagnosis or a validated medical device: the result points you toward a professional.
• Hydroxyurea follow-up test reminder : Trévor works out the date of your next follow-up test by adding the pace your doctor gave you to the date of the last known test. It never suggests a pace itself and sends no reminder until you have entered one.
• Hydroxyurea in the crisis risk : When you take hydroxyurea, your regularity over the last 84 days becomes two features of the risk model: a protective one and an "irregular intake" one. This card describes only that input, not the full risk calculation, which has its own card.
• Hydroxyurea regularity (days covered) : Trévor counts, over the last 12 weeks, the share of logged days on which you took your hydroxyurea. This percentage helps you see how regular you are and feeds other indicators (crisis signal, crisis risk). It is not a validated medical device and it does not judge how you take your treatment.
• "Worth discussing with your team" signal (HbF or crises) : Trévor spots two situations worth raising with your care team: an HbF that stays under your own best level over three measurements, or at least three crises in six months despite regular intake. It never concludes that the treatment does not work and proposes no change.
• How a day is classed as a "crisis" day : Trévor decides whether a day counts as a crisis day from what you logged: severe pain, hospitalization, a declared crisis episode. This label is then used to train the risk model, to spot trends and to test associations. The rules are not identical in every module.
• Reminder the day before your crisis-prone weekday : If at least 5 of your crises over the last 120 days cluster on the same weekday, Trévor spots that day so it can send a self-care reminder the day before. It relies only on your own journal.
• Pain check after a rescue painkiller : 45 minutes after you log a rescue painkiller dose, Trévor asks how the pain is and applies a three-level escalation protocol: call the emergency number (144 in Switzerland), go to the ER, or medical advice within 24 hours. The thresholds remain to be validated by hematology. This is not a validated medical device.
• "Default" doses and treatment regularity rate : When you are in "exception" mode, Trévor shows your treatments as taken until you report a missed dose, and writes an "assumed" taken row overnight. The regularity rate of each treatment is then computed on logged days.
• Questions to ask your doctor : Trévor prepares up to five questions for your appointment from your recent data: crises, regularity, hydroxyurea signal, late transfusion, wound, overdue exams. Each question points to a topic to raise, never a diagnosis.
• Questionnaire scores: self-efficacy, quality of life, perceived usefulness : Trévor computes the score of several questionnaires: confidence in managing your condition (9 to 45), EQ-5D-5L quality of life, PedsQL quality of life (0 to 100) and perceived usefulness of Trévor (USE scale or short 3-question questionnaires). Each score is saved with your answer. These are not validated medical devices.
• Medicine stock and reorder reminder : Trévor estimates how many treatment days you have left for each medicine and offers to prepare an order when stock gets low. It sends nothing to the pharmacy without your agreement.
• Perceived stress: PSS-10 scale and daily feeling : Trévor computes your score on the PSS-10 perceived stress scale (0 to 40) and gives it a level, then reacts to your daily feeling (0 to 10) with advice. The questionnaire cannot be retaken within 14 days. This is not a diagnosis or a validated medical device: the result points you toward a professional.
• Spaced "how are you?" and assumed values : Trévor does not ask you every day how you are. By default it assumes all is well as long as you say nothing, and asks one short question from time to time, more spaced out when you answer "good". Assumed days are never used as evidence.
• Prevention follow-up, vaccines and exam reminders : For each monitoring exam or vaccine you follow, Trévor computes the due date (last date + interval) and a state: up to date, soon, overdue or never entered. It sends a gentle reminder, only one per due date.
• Insights on your crises and regularity : Over 120 days, Trévor compares the number of your crises this month and last month, your sleep before crises, the most frequent weekday, your regularity per treatment, and well- versus poorly-followed weeks. These are descriptive observations, never proof of cause.