Patients receiving vitamin K antagonists (VKAs), particularly those with mechanical heart valves, need an individual INR target, regular dose review and clear communication between caregivers and clinicians. Current guidelines emphasise the importance of well-managed anticoagulation [2]. A systematic review has shown that maintaining INR within the therapeutic range remains difficult in sub-Saharan Africa [3]. This supports closer examination of how treatment is monitored in routine practice. Our study will assess whether CoaguCarnet® is associated with more complete documentation and continuity of follow-up.

At the SSRCV, patients taking VKAs have traditionally used a folded sheet to record their INR results and dose changes. Space for documenting successive visits is limited. CoaguCarnet® was developed as a 31-page booklet containing INR results, prescribed doses, appointment dates, consultation notes, practical advice and contact details. It drew on French patient-education and VKA monitoring booklets, adapted to how anticoagulation care is organised in our service. The original documents and their conditions of reuse still need to be confirmed. The booklet is being studied as an organisational intervention informed by the Medical Research Council framework [4]. Previous research on anticoagulation education provides a rationale for evaluating patient-facing tools, although findings from other settings may not apply directly here [5][6].

Primaryobjective. To estimate the adjusted difference between cohorts in the mean patient-level Clinical Traceability Index (CTI; 0 - 5) over six months from each patient’s index visit. The CTI will be scored only from the original monitoring document. This outcome measures the quality of the record, not the effect of the booklet on bleeding, thrombosis or other clinical outcomes.

Secondarycomparativeobjectives. To examine the availability and completeness of the original monitoring records, including longitudinal INR results, prescribed doses and documented medical follow-up. We will assess whether the available INR measurements allow calculation of time in therapeutic range (TTR) according to predefined rules. Recorded bleeding, thrombotic events and other complications will be reviewed only where the information is sufficiently comparable between cohorts.

Prospective-onlyobjectives. Among patients using CoaguCarnet®, we will assess understanding of anticoagulant treatment, satisfaction with the booklet, its use during follow-up and whether patients bring it to appointments. We will also record how well the booklet holds up over time, gather healthcare professionals’ impressions of it, and time how long it takes to review a patient’s treatment history. Medication adherence will be measured only if a validated French-language questionnaire is available. The Adherence to Refills and Medications Scale (ARMS) is one candidate [7], though its use here depends on confirming a suitable French-language version and its conditions of use.

This single-centre ambispective study will compare a historical cohort using the conventional sheet with a prospective cohort using CoaguCarnet®. All eligible historical patients whose first qualifying visit occurred between 1 January and 31 March 2026 will be included. Prospective recruitment will aim for 75 consecutive patients from 15 October 2026, subject to institutional activation. Patients will not be randomly assigned to either group. For each patient, follow-up will begin at the first eligible INR monitoring visit during the recruitment period; those attending more than once will be included only once. Both cohorts will be followed or reconstructed for six months from that date (Table 1, Figure 1).

Because the two recruitment periods are separate, the same person may be eligible in both. Such a patient may contribute one observation to each cohort, but only once within each period. A stable study identifier will flag anyone re-enrolling across cohorts. In the primary patient-level regression, two observations from the same person will be treated as correlated, with Huber-White standard errors clustered by patient identifier. A sensitivity analysis restricted to patients in only one cohort will also be reported.

The historical observation period will end before the new booklet is introduced. We will document staffing changes, interruptions in INR reagent supply, laboratory procedures, clinic schedules, educational activities and other changes to routine care during both periods.

Table 1.Ambispective design: cohort identification and observation windows.

Figure 1. Ambispective study flow. The historical conventional-sheet cohort comprises all eligible patients with index encounters from 1 January to 31 March 2026; the prospective CoaguCarnet® cohort targets 75 consecutive patients, with a planned start on 15 October 2026. Observation lasts six months from each patient’s index date. Non-retrieved original supports are missing, not zero, in the primary analysis. The schematic contains placeholders for actual screening and analysis counts; these must be completed when available. The July 2026 institutional authorisation covers the retrospective records used here.

Commoneligibilitycriteria. age ≥ 18 years on index date; documented VKA prescription and indication; participation in SSRCV INR follow-up; an identifiable index encounter; and sufficient unique identifiers in the source system to deduplicate records. For the historical cohort, we will include all eligible patients, including those who have died, stopped attending follow-up visits, or have incomplete records. Patients will not need to have undergone a minimum number of INR tests after inclusion. In the prospective cohort, patients will be informed about the study and asked to provide their consent before enrolment, following the approved study procedures.

Historicalidentification. We will review the anticoagulation follow-up register for January to March 2026 to identify all patients who meet the study criteria. Patients who attended more than once during this period will be counted only once. We will record the number of patients screened, how many met the eligibility criteria, and the reasons why some were not included.

Prospectiveidentification. We will record all patients considered for the prospective cohort, including those who decline to participate or are not enrolled for other reasons. Cohort assignment will be based on the monitoring document used at the first eligible visit. Patients who do not complete the six-month follow-up will remain in the cohort, and the reasons for incomplete follow-up will be recorded whenever available. Death, transfer, a change of anticoagulant or loss to follow-up will not be used to exclude patients retrospectively.

Historicalstandardcare. the conventional folded VKA monitoring sheet, with usual prescribing and INR assessment.

Prospectiveintervention. Each participant will receive a 31-page CoaguCarnet® booklet, accompanied by a brief standard explanation and demonstration of an INR entry. Patients will be encouraged to bring it to their appointments. Anticoagulant dosing and other clinical decisions will remain with the treating clinicians. Training time and any additional education will be recorded. To describe implementation, we will document booklet distribution, availability at visits, staff orientation and the use of designated sections. Copies of both monitoring supports and the teaching materials will be retained as study materials, subject to clarification of reproduction rights. Staff instructions will not suggest that one support is superior.

The schedule of measurements for each cohort is summarised in Table 2.

Table 2.Measurement schedule by cohort and time point.

Selectionbias. The historical register will be reviewed exhaustively, while prospective patients will be recruited consecutively. Completion of six-month follow-up will not be a condition for remaining in either cohort.

Periodeffects. Staffing, INR testing procedures, supply availability and the organisation of care will be reviewed for changes between the two periods. Other developments that could have affected follow-up will also be noted. Where the information permits, these factors will be considered in the analysis, although adjustment cannot fully separate the booklet from changes over time.

Hawthorneeffect. Healthcare professionals will know that CoaguCarnet® is being evaluated. CTI scores will therefore not be shared with the care team during follow-up, and staff will receive the same instructions for using the booklet. Monthly CTI patterns will be examined to see whether documentation changes over the six months. This cannot rule out the influence of being observed on routine recording practices.

Informationbias. Both cohorts will be assessed using the same scoring rules. Copies of original monitoring documents will be anonymised and presented to reviewers in random order. Patient identities and clinical outcomes will be concealed from the reviewers where possible, although the layout of each document may reveal the group. Retrieval rates will be reported separately, and a second reviewer will verify data extracted from the anticoagulation register against the source records.

Confounding. Baseline adjustment variables will be taken from information available before or at the index visit in both cohorts: age in years; sex; VKA indication (mechanical heart valve versus other); VKA treatment duration at index in months; prior anticoagulation control, defined as the proportion of INR results within the patient’s target range in the 90 days before index, with a separate indicator for patients having no pre-index INR; and prior monitoring frequency, the number of INR visits in that same 90-day window. Variables that may have shifted as a result of CoaguCarnet® use will not be used for baseline adjustment. Period-level service changes will be described and considered only in prespecified sensitivity analyses, since they may be incompletely measured. A bias and missingness audit checklist is provided in Appendix B.

We plan to recruit 75 patients into the prospective cohort during routine follow-up visits. This number reflects the number of patients we expect to enrol at our service, rather than a formal sample-size calculation. In the historical cohort, all eligible patients identified in the register between 1 January and 31 March 2026 will be included, each counted once. We will not reduce that group to match the prospective target. After the record review, both the total number eligible and the number with sufficient data for CTI analysis will be reported.

Before analysis of the prospective data, a pilot review of approximately 30 historical patients selected across January, February and March 2026 will estimate the mean patient-level CTI, its standard deviation and distribution, the retrieval rate of original sheets, and the number of INR visits per patient. These estimates will inform a sensitivity-based assessment of power and precision using a two-sided alpha of 0.05, 80% target power (with a 90% scenario), the historical cohort size and unequal allocation. A difference of one CTI point out of five is a provisional operational threshold that must be justified before prospective outcomes are inspected. The calculations will account for the expected proportion of evaluable prospective records. If 75 patients do not offer adequate power or precision, the study will emphasise adjusted differences and 95% confidence intervals rather than claims of superiority or equivalence. The pilot will not be used to select an effect size that favours a particular result.

Two reviewers will independently score at least 20 historical sheets and 20 CoaguCarnet® booklets, including records with differing levels of completeness where possible. Agreement on each CTI item will be reported as a percentage and with Cohen’s kappa, interpreted in light of item prevalence. For the total score, we will calculate an absolute-agreement intraclass correlation coefficient (ICC) with a 95% confidence interval. Differences will be discussed after independent scoring, and any clarification of the rules will be made before the main dataset is locked. This pilot will show how consistently reviewers apply the CTI scoring criteria, although it will not establish the clinical validity of the score.

Patient characteristics will be described separately for each cohort. We will use descriptive statistics and standardised differences to assess how the groups compare at baseline, without relying solely on p-values. We will report numbers screened and enrolled, index visits, original documents retrieved, INR visits with a CTI score, follow-up person-time and reasons for missing data. Patient-level CTI will be described using means and standard deviations, medians and interquartile ranges, and the proportions with a mean score of exactly 0 or 5.

Primaryanalysis

The primary comparison uses ordinary least-squares linear regression, with each cohort-period patient’s mean CTI across scored visits as the outcome. The model includes study group (prospective CoaguCarnet® versus historical conventional sheet) and the prespecified baseline covariates: age in years, sex, VKA indication (mechanical heart valve versus other), VKA treatment duration in months, the proportion of INR results within target in the 90 days before index plus an indicator for no pre-index INR, and the number of INR visits in that same 90-day window. Standard errors will be clustered by patient identifier (Huber-White), so that someone appearing in both cohorts is not counted as two independent observations. The effect measure is the adjusted mean difference in CTI (prospective minus historical), with a 95% confidence interval and p-value. The regression uses observations with a non-missing CTI and the required covariates; the amount and pattern of covariate missingness will be reported, and multiple imputation examined in sensitivity analysis if its assumptions hold. Residuals and influential observations will be checked; if linear-model assumptions are materially inadequate, patient-level bootstrap confidence intervals will be reported as a sensitivity analysis. A supplementary visit-level mixed-effects model with a patient random intercept will account for repeated visits within patients.

Sensitivityanalyses

Sensitivity analyses will test whether findings depend on the scoring rules or on record availability: a score restricted to items recordable on both supports, a scenario assigning zero to visits without a retrieved original (not read as evidence of poor care), and an analysis restricted to patients with complete records. We will also examine the monthly CTI pattern during prospective follow-up, try alternative baseline adjustments, and repeat the comparison among patients with similar VKA indications. For TTR, a separate analysis applies a 42-day maximum interval between INR measurements. We will also repeat the primary comparison after excluding patients who contributed to both cohort periods.

Missingdataandsecondaryoutcomes

Missing information will be classified as never recorded, illegible, original support not found, clinically unavailable, or not applicable for non-CTI variables. For the primary CTI, all five items are applicable by definition; a non-retrieved original is coded as missing source rather than zero, and a patient with no scorable encounter has a missing patient-level CTI. We will describe the extent and reasons for missing data in each cohort. Because records may be less complete or harder to retrieve in one group than the other, a complete-record analysis alone could bias the result. Multiple imputation will be considered for missing covariates when the data, sample size and assumptions allow; the primary CTI itself will not be imputed from the clinical register.

We will also compare how many patients have enough information to calculate TTR, reporting the risk difference with a 95% confidence interval. These figures will be read together with the frequency of INR testing and the share of follow-up covered by interpolation.

Bleeding, thrombotic events, related hospitalisations and deaths will be given as event counts and as rates per observed person-time. Since these events may have been recorded differently in the historical and prospective periods, the comparisons will stay exploratory. Knowledge, adherence (where a validated questionnaire is available), satisfaction and booklet durability will be described within the prospective cohort. Time taken to reconstruct treatment history will be compared between cohorts only if an equivalent timed assessment can be applied, with reviewers blinded wherever feasible.

The Direction Médicale et Scientifique (DMS) of the Institut de Cardiologie d’Abidjan (ICA) granted institutional approval in July 2026 within the CoaguloCare programme, according to the study’s institutional record. This is a non-invasive documentation intervention and does not require protocol-directed changes in VKA treatment. This approval covers the use of retrospective monitoring records and the applicable consent requirements. Prospective participants will receive information about the study and give informed consent before enrolment, in line with the approved procedures. Each patient will be given a study code, and the file linking these codes to patients will be kept separately, with access restricted to authorised members of the research team. Any current anticoagulation safety concern identified during follow-up will be referred to the treating clinicians.

This is a protocol of a non-randomised observational comparison, not a randomised trial. STROBE will guide reporting of the completed cohort results [10], RECORD will supplement reporting of routinely recorded retrospective data [11], and the Medical Research Council framework will inform description and evaluation of the complex intervention [4]. SQUIRE 2.0 may further inform description of the local service-improvement context [12], without being treated as the governing protocol standard. The booklet’s French educational antecedents will be acknowledged, and any third-party copyrighted materials will be reproduced only where rights permit. No clinical efficacy claim will be made from documentation outcomes alone.

The comparison has several limitations. Patients come from different periods, healthcare professionals cannot be blinded to the booklet, and the CTI is a new score whose validity has not been established. Some original monitoring records may be missing, and bleeding or thrombotic events may have been captured unevenly across the two cohorts, which could affect the results. The study will test whether CoaguCarnet® is associated with more complete documentation of anticoagulation care in our setting; any gain seen, however, may also come from shifts in routine practice rather than from the booklet alone. A higher CTI score cannot be taken as evidence of fewer bleeding or thrombotic events.

Approved by the Direction Médicale et Scientifique, Institut de Cardiologie d’Abidjan, in July 2026, within the CoaguloCare programme; see Section 11 for scope and consent procedures.

Boka BC conceived and designed the study, designed the statistical analysis plan and drafted the manuscript. Coffie P, Hauhouot M-L and Ekou KA supervised the work. Flainde LD and Yeo A were responsible for data collection. Oga S contributed to supervision and critical revision. All authors reviewed and approved the final manuscript.

No study results are reported in this protocol. Access conditions for future de-identified study data will follow institutional approvals.

Rules. Score the CTI from the original paper support only. A zero is not the same as “source not retrieved,” coded separately as NA-SOURCE. All five items apply to every eligible INR encounter, so NA-RULE is not used in the primary score and the denominator stays five. If an assessor considers an item genuinely non-applicable, the encounter is flagged for adjudication and its total CTI stays missing until the decision is resolved. The INR item needs a numerical value; decimal-point and decimal-comma notation are accepted, qualitative-only terms are not. For each control, record source retrieval, the five-item CTI vector, total score, assessor ID and adjudication status. Keep an item-level scoring log and a prespecified random reassessment sample.

☐ Historical register denominator and unique-patient deduplication verified

☐ Original folded sheets retrievable for each scheduled/recorded INR encounter

☐ Same index definition and six-month follow-up anchor applied to both groups

☐ Staffing, testing capacity, INR reagent supply and workflow change log collected

☐ Baseline covariates measured in both cohorts and overlap checked

☐ Inter-rater reliability pilot completed without exposure to group-level results

☐ Primary versus common-core and missing-source sensitivity analyses locked

☐ Prospective training script and monthly fidelity monitoring archived

☐ Prospective consent and historical-record ethics decision documented

☐ Data sources and clinical-event ascertainment limitations reported