Clinical Report: When NPi and QPi Diverge: Does QPi Add Prognostic Value?

Overview

The prospective, multicentre LYNX study found that NPi and QPi were correlated and each was associated with six-month neurological outcomes, but QPi was more sensitive to anaesthetic exposure. The supplied commentary notes that these findings do not establish whether abnormal QPi readings when NPi is normal add prognostic information beyond NPi and conventional clinical assessment.

Background

Automated pupillometry provides quantitative measures used in the assessment of patients with acute brain injury. In LYNX, the neurological pupil index (NPi) and quantitative pupil index (QPi) were compared using paired measurements, allowing their relationship and differing responses to be examined. The distinction between association with outcome and incremental prognostic information matters when interpreting discordant readings. The source also cautions that the threshold of 3 was established for NPi, not QPi.

Data Highlights

Key Findings

• LYNX was a prospective, multicentre study comparing NPi and QPi in patients with acute brain injury.
• The indices showed moderate-to-strong correlation across 7,089 paired measurements (r = 0.717).
• Abnormal measurements were more frequent with QPi than NPi: median proportions were 12.7% and 1.2%, respectively.
• In separate adjusted models, both indices were independently associated with unfavourable six-month neurological outcomes; the reported analyses do not establish incremental prognostic value of QPi beyond NPi.
• The commentary identifies abnormal QPi with normal NPi as a discordance requiring further assessment, including its frequency, persistence, and relationship to later outcomes.
• Because anaesthetic exposure markedly reduced QPi and the threshold of 3 was established for NPi rather than QPi, discordant readings require interpretation in the context of pharmacological exposure; comparisons using that threshold for QPi are exploratory.

Clinical Implications

The source supports interpreting NPi and QPi as non-interchangeable measures and considering anaesthetic exposure when evaluating QPi. It does not establish that QPi adds prognostic information when NPi is normal; the proposed assessment of discordant readings is exploratory.

Conclusion

LYNX demonstrates that NPi and QPi are correlated yet differ in the frequency of abnormal readings and sensitivity to anaesthetic exposure. Whether QPi–NPi discordance provides prognostic information beyond NPi remains unresolved in the supplied material.

Related Resources & Content

1. Bouzat et al., Critical Care, 2026 — Comparison of two automated pupillometry indices in patients with acute brain injury: the prospective multicentre LYNX cohort study
2. ASCO Publications — Comparison between two prognostic index: Nottingham index (NPI) and an alternative index based on log of nodal involvement (Lpi)
3. ASCO Publications — Retrospective application of Nottingham Prognostic Index (NPI) and Adjuvant! Online tool in newly diagnosed patients with early breast cancer in mid-western Ireland.
4. ASCO Publications — Prognostic impact of post-prostatectomy PSA slope determined with a novel, nucleic acid detection immunoassay (NADiA ProsVue) for total PSA.
5. ASCO Publications — Prognostic impact of post-prostatectomy PSA slope determined with a novel, nucleic acid detection immunoassay (NADiA ProsVue) for total PSA.
6. Comparison of two automated pupillometry indices in patients with acute brain injury: the prospective multicentre LYNX cohort study
7. Comparison of two automated pupillometry indices in patients with acute brain injury: the prospective multicentre LYNX cohort study | Critical Care | Springer Nature Link
8. Prognostic value of automated pupillometry in traumatic brain injury: a systematic review and meta-analysis.
9. The Brussels consensus for non-invasive ICP monitoring when invasive systems are not available in the care of TBI patients (the B-ICONIC consensus, recommendations, and management algorithm) - PubMed