REVIEW 3 major objections 5 minor 37 references
The Anatomy of Evidence: An Investigation Into Explainable ICD Coding
T0 review · 3 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read Proximity-aware match measures show explainable ICD models align with human evidence in about 80% of test cases.
desk verdict A useful, honest evaluation paper with new match measures and dataset analyses; the 80% headline is recall-oriented, and the lack of a precision baseline is the main gap. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is a taxonomy of five match measures that compare model-extracted evidence spans against ground truth spans: Empty (no evidence predicted), Exact (the sets of spans are equal), Proximate (every ground truth span has at least one matching token and all unmatched tokens fall within a context window of k=10 tokens), Partial (at least one ground truth span lacks a match or some model tokens fall outside the context window), and No match (no token overlap). This taxonomy carries the evaluation argument because it treats evidence as useful when it guides attention to the right context window, rather than requiring exact span equality as F1 and IOU do. The supporting machinery is the MDACE dataset with its sufficient and complete code-evidence annotations, the PLM-ICD-based architecture modified with standard cross-attention, and the AttInGrad feature attribution method (attention weights multiplied by input-times-gradient scores) with a threshold chosen on the validation set.
What would settle it
Re-annotate a random sample of the 61 test discharge summaries with an independent team of professional coders under the same guidelines, then compute inter-annotator agreement between the new annotations and the MDACE spans; if that agreement is no higher than the supervised model's match rate on the same documents, the ground truth is too noisy to support the paper's comparative claims.
Extended reading notes
Core claim
The central claim is that current explainable ICD coding models, when evaluated with proximity-aware match categories instead of F1/IOU, align substantially with human-annotated evidence: the best supervised model achieves some form of match (exact, proximate, or partial) in about 80% of test cases, with relatively few empty or no-match predictions. The supervised approach, which uses annotated evidence in its training objective, yields more exact matches and fewer empty and no-match cases than an unsupervised baseline that only regularizes gradients. The paper also finds that human evidence is not systematically located at the document start, that many codes have little overlap between evidence and their official descriptions, and that the 'sufficient' (Inpatient) annotation scheme is not a subset of the 'complete' (Profee) scheme in the common documents. These findings support a recommendation for investment in evidence annotation when exact matches are desired, and for reporting false positives in future evaluation.
Load-bearing premise
The evaluation assumes that the MDACE human-annotated evidence spans are a complete and reliable gold standard, and that the 61-document test set with 586 evidence spans, together with one selected model seed per training strategy, is enough to compare supervised versus unsupervised evidence extraction.
Editorial extensions
If this is right
- If the central claim holds, supervised training with evidence annotations should be the recommended strategy when deployment requires exact or near-exact evidence matches, and investing in evidence annotation is a concrete way to improve that outcome.
- The proximity-aware match measures constitute a ready-to-use evaluation protocol for explainable medical coding that is more interpretable to end users than F1 or IOU, and can be adopted as a default reporting standard alongside existing metrics.
- The finding that many codes have high overlap between evidence and code descriptions suggests that a subset of the ICD coding task can be solved efficiently with rule-based or hybrid approaches, freeing deep learning for the harder, low-overlap codes.
- The observed relationship between short model evidence and lower recall indicates that explanation length can serve as a lightweight warning signal for likely classification errors in deployed systems.
- The low probabilities associated with empty evidence predictions and the absence of a probability signal for exact matches give a concrete direction for future work on model calibration and its interaction with explanation quality.
Reading between the lines
- A natural extension of the match taxonomy would be to apply it to other evidence-extraction tasks in clinical NLP, such as procedure coding or coding in languages other than English, where the same proximity semantics could guide evaluation design.
- The 80% overlap figure is dominated by partial matches; if a stricter bar requiring exact or proximate matches were used, the practical usefulness of current models would appear considerably lower, which is worth stating explicitly when comparing systems.
- The paper's observation that models extract drugs and co-morbid conditions as evidence for diagnoses suggests that feature attribution methods reflect correlational rather than causal structure; regulatory acceptance of such explanations may require additional causal or counterfactual validation.
- The finding that sufficient evidence is not a subset of complete evidence, while the authors attribute it to different coding rules, may also indicate that the annotation guidelines themselves need formalization before a single gold standard can be assumed for benchmark comparisons.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper analyzes the MDACE dataset and evaluates current explainable ICD coding models. It studies where human-annotated evidence is located, how much evidence overlaps with code descriptions, and whether sufficient evidence is a subset of complete evidence. For model evaluation, it introduces match measures (empty, exact, proximate, partial, no match) and reports that the best supervised model identifies at least one correct token in roughly 80% of test cases, with supervised training producing more exact matches and fewer empty or non-matches than an unsupervised input-gradient-regularization model. The paper closes with recommendations for practitioners and researchers, including the reporting of false positives.
Significance. If substantiated, the paper offers a useful application-oriented evaluation protocol for evidence extraction in medical coding and a helpful characterization of the MDACE dataset. The strengths are the public code, the transparent match counts, the explicit split and seed details, and the qualitative error analysis. However, the headline overlap figure and the supervised-versus-unsupervised comparison depend on permissive match definitions and on a single selected seed per training strategy, and the paper does not yet provide a baseline or precision analysis that would show the match measures capture evidence quality better than F1/IOU. The contribution is therefore potentially valuable to the community, but the central empirical claims need additional support before the recommendations can be taken as established.
major comments (3)
- [§4.3, §4.1, §4.5] The headline 80% overlap result counts exact, proximate, and partial matches as success, but the proximate and partial definitions are very permissive. Proximate requires each ground-truth sequence to share at least one token, with unmatched tokens inside a context window of k=10; partial is triggered whenever at least one ground-truth sequence is unmatched or any machine token falls outside the window. No constraint limits the total number of machine-extracted tokens or false positives, and §4.5 itself notes that models "tend to extract more evidence than humans annotated, often echoing the same or similar information at different positions." Without a trivial high-recall baseline (e.g., top-k attribution tokens or all tokens above a low threshold) and without precision or false-positive counts per match type, the 80% figure and the claim that the proposed measures are more meaningful than F1/IOU are not established; the results may reflect extraction breadth rather than evidence quality.
- [§4.1, §5.1, Appendix C.1] The comparison between supervised and unsupervised training strategies is based on one seed per strategy, selected according to explanation metrics. Because ten model seeds are available for each strategy and Figure 8 shows nontrivial variation across seeds in F1, precision, and recall, the observed differences in exact, empty, and no-match counts cannot currently be attributed to the training strategy rather than to the selected seed or to selection effects. The recommendation that investing in evidence annotation improves exact matches would require an aggregate comparison over seeds with appropriate error bars or a paired statistical test.
- [§4.3] The semantic relabeling of no-match cases was performed by two authors with "basic medical knowledge," without inter-annotator agreement and without considering the surrounding context; the authors themselves state that expert assessments are necessary. The reported 46% and 53% "semantically meaningful" rates should therefore be treated as exploratory and should not carry quantitative weight in the narrative that model evidence is closer to human evidence than token-level matching suggests.
minor comments (5)
- [§3.3] "we selected the 52 document with common hospital admission ID" appears to be a typo for "52 documents."
- [Figure 6] The figure uses the abbreviation "prox." while the text defines "proximate"; please use the same term consistently.
- [Figure 5] The figure caption does not identify the blue/orange color scheme that the text refers to; a legend or explicit caption labels would improve readability.
- [§4.4] The 74% agreement figure is computed for two selected seeds; the text should state explicitly that this is a seed-specific observation rather than a property of the training strategies in general.
- [§5, Limitations] The fixed context window k=10 is acknowledged in the limitations, but a short sensitivity analysis varying k would substantially strengthen the proximate-match definition.
Circularity Check
No significant circularity: the evaluation uses external human-annotated evidence and independently defined match measures; disclosed threshold dependence is a limitation, not a circular step.
full rationale
The paper's central claims—that human-annotated evidence aligns with code descriptions to a certain degree, and that supervised evidence extraction achieves high overlap with ground truth under proximity-aware match measures—are evaluated against the externally produced MDACE dataset (Cheng et al., 2023), not against quantities defined by the paper's own conclusions. The proposed match measures (empty, exact, proximate, partial, no match) are defined independently of the models being evaluated and are computed from token overlap between model attributions and human-annotated spans; this is a standard external plausibility evaluation rather than a self-definitional exercise. The 80% overlap figure in Section 4.3 is an empirical count on the held-out test set, not a fitted parameter or an identity derived from the measure definitions. The paper's self-citations (Antweiler et al., 2023; Klug et al., 2024; Müller et al., 2023) and the use of Edin et al. (2024) models are contextual or comparative and do not carry the weight of the main evidence. The one disclosed dependence—that the unsupervised model's attribution threshold is set using annotated evidence (Section 5.1: 'The unsupervised training strategy with input gradient regularization proved similarly successful as the supervised approach, the annotated evidence was still used to compute a feature attribution threshold')—is an honest limitation that weakens the interpretation of the unsupervised comparison, but it does not make the match-rate results circular, since the threshold is a calibration choice and the match rates are still measured against external ground truth. Likewise, the permissiveness of proximate/partial matches is a methodological concern about whether the measure captures usable evidence quality, not a circularity in the derivation. No step was found where a predicted quantity is equivalent by construction to an input or where a load-bearing premise reduces to a self-citation chain.
Assumptions & free parameters
free parameters (3)
- Proximate match context window k =
10
- Code prediction probability threshold =
0.5
- AttInGrad attribution decision threshold =
not reported
assumptions (3)
- domain assumption Human-annotated evidence spans in MDACE are a valid gold standard for explanation plausibility.
- domain assumption Feature attribution scores from AttInGrad are meaningful indicators of model evidence.
- ad hoc to paper A single seed per training strategy is representative for comparing supervised versus unsupervised evidence extraction.
Cite this review
Pith. "Pith review of The Anatomy of Evidence: An Investigation Into Explainable ICD Coding." pith.science (2026). https://pith.science/paper/P76DQHNT
@misc{pith2026250701802,
author = {Pith},
title = {Pith review of: The Anatomy of Evidence: An Investigation Into Explainable ICD Coding},
year = {2026},
howpublished = {\url{https://pith.science/paper/P76DQHNT}},
note = {Machine review of arXiv:2507.01802}
}
read the original abstract
Automatic medical coding has the potential to ease documentation and billing processes. For this task, transparency plays an important role for medical coders and regulatory bodies, which can be achieved using explainability methods. However, the evaluation of these approaches has been mostly limited to short text and binary settings due to a scarcity of annotated data. Recent efforts by Cheng et al. (2023) have introduced the MDACE dataset, which provides a valuable resource containing code evidence in clinical records. In this work, we conduct an in-depth analysis of the MDACE dataset and perform plausibility evaluation of current explainable medical coding systems from an applied perspective. With this, we contribute to a deeper understanding of automatic medical coding and evidence extraction. Our findings reveal that ground truth evidence aligns with code descriptions to a certain degree. An investigation into state-of-the-art approaches shows a high overlap with ground truth evidence. We propose match measures and highlight success and failure cases. Based on our findings, we provide recommendations for developing and evaluating explainable medical coding systems.
Figures
Figures from the paper (4 more)
Reference graph
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Reviewed August 6, 2026 · model on record in the stance chip above.
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