tetano
Editor, Senior Moderator
Int J Infect Dis
. 2026 Apr 13:108703.
doi: 10.1016/j.ijid.2026.108703. Online ahead of print.
Positive Predictive Value of Respiratory Infection Diagnoses in The Danish National Patient Registry: a Post-hoc Validation Analysis of the DANFLU-1 Trial
Jacob Christensen[SUP] 1 [/SUP], Niklas Dyrby Johansen[SUP] 1 [/SUP], Katrine Feldballe Bernholm[SUP] 1 [/SUP], Julie Inge-Marie Helene Borchsenius[SUP] 1 [/SUP], Kira Hyldekær Janstrup[SUP] 1 [/SUP], Daniel Modin[SUP] 1 [/SUP], Kristoffer Grundtvig Skaarup[SUP] 1 [/SUP], Joshua Nealon[SUP] 2 [/SUP], Sandrine Samson[SUP] 2 [/SUP], Matthew Loiacono[SUP] 3 [/SUP], Youjun Huang[SUP] 4 [/SUP], Rebecca Harris[SUP] 5 [/SUP], Carsten Schade Larsen[SUP] 6 [/SUP], Anne Marie Reimer Jensen[SUP] 1 [/SUP], Nino Emanuel Landler[SUP] 1 [/SUP], Brian L Claggett[SUP] 7 [/SUP], Scott D Solomon[SUP] 7 [/SUP], Gunnar H Gislason[SUP] 8 [/SUP], Lars Køber[SUP] 9 [/SUP], Martin J Landray[SUP] 10 [/SUP], Pradeesh Sivapalan[SUP] 11 [/SUP], Jens Ulrik Stæhr Jensen[SUP] 11 [/SUP], Tor Biering-Sørensen[SUP] 12 [/SUP]
Affiliations
Objectives: To validate respiratory infection diagnosis codes in the Danish National Patient Registry (DNPR) in the DANFLU-1 feasibility trial, and to assess whether reperforming effectiveness analyses with validated events altered findings.
Methods: Hospitalizations for influenza or pneumonia (ICD-10 codes J09-18) were validated against medical chart review by two blinded physicians. Events were validated against 1) medical opinion and 2) diagnostic criteria of symptomatology combined with laboratory or radiological verification. Positive predictive values (PPV) were calculated along with relative vaccine effectiveness (rVE) of high-dose (HD) vs. standard-dose (SD) influenza vaccines.
Results: Among 12,477 participants, we identified 43 events in the DNPR (influenza J09-11: n=3, pneumonia J12-18: n=40), which demonstrated a PPV of 86% (95% CI; 72%-95%) and 91% (78%-97%) against the medical opinion of the respective reviewers. Against diagnostic criteria, the PPV was 65% (49%-79%) and 67% (51%-81%). For influenza codes, the PPV was 100% according to both reviewers and references, and between 63% and 90% depending on reviewer and reference for pneumonia. The rVE consistently favored HD vs. SD against validated events.
Conclusion: Hospitalizations for pneumonia registered in the DNPR may benefit from subsequent validation, warranting further studies. HD influenza vaccination was associated with fewer validated events compared with SD.
Keywords: DANFLU-1; Danish National Patient Registry; High-dose influenza vaccine; ICD-10; INFLUENZA; Pneumonia; Positive predictive value.
. 2026 Apr 13:108703.
doi: 10.1016/j.ijid.2026.108703. Online ahead of print.
Positive Predictive Value of Respiratory Infection Diagnoses in The Danish National Patient Registry: a Post-hoc Validation Analysis of the DANFLU-1 Trial
Jacob Christensen[SUP] 1 [/SUP], Niklas Dyrby Johansen[SUP] 1 [/SUP], Katrine Feldballe Bernholm[SUP] 1 [/SUP], Julie Inge-Marie Helene Borchsenius[SUP] 1 [/SUP], Kira Hyldekær Janstrup[SUP] 1 [/SUP], Daniel Modin[SUP] 1 [/SUP], Kristoffer Grundtvig Skaarup[SUP] 1 [/SUP], Joshua Nealon[SUP] 2 [/SUP], Sandrine Samson[SUP] 2 [/SUP], Matthew Loiacono[SUP] 3 [/SUP], Youjun Huang[SUP] 4 [/SUP], Rebecca Harris[SUP] 5 [/SUP], Carsten Schade Larsen[SUP] 6 [/SUP], Anne Marie Reimer Jensen[SUP] 1 [/SUP], Nino Emanuel Landler[SUP] 1 [/SUP], Brian L Claggett[SUP] 7 [/SUP], Scott D Solomon[SUP] 7 [/SUP], Gunnar H Gislason[SUP] 8 [/SUP], Lars Køber[SUP] 9 [/SUP], Martin J Landray[SUP] 10 [/SUP], Pradeesh Sivapalan[SUP] 11 [/SUP], Jens Ulrik Stæhr Jensen[SUP] 11 [/SUP], Tor Biering-Sørensen[SUP] 12 [/SUP]
Affiliations
- PMID: 41985620
- DOI: 10.1016/j.ijid.2026.108703
Objectives: To validate respiratory infection diagnosis codes in the Danish National Patient Registry (DNPR) in the DANFLU-1 feasibility trial, and to assess whether reperforming effectiveness analyses with validated events altered findings.
Methods: Hospitalizations for influenza or pneumonia (ICD-10 codes J09-18) were validated against medical chart review by two blinded physicians. Events were validated against 1) medical opinion and 2) diagnostic criteria of symptomatology combined with laboratory or radiological verification. Positive predictive values (PPV) were calculated along with relative vaccine effectiveness (rVE) of high-dose (HD) vs. standard-dose (SD) influenza vaccines.
Results: Among 12,477 participants, we identified 43 events in the DNPR (influenza J09-11: n=3, pneumonia J12-18: n=40), which demonstrated a PPV of 86% (95% CI; 72%-95%) and 91% (78%-97%) against the medical opinion of the respective reviewers. Against diagnostic criteria, the PPV was 65% (49%-79%) and 67% (51%-81%). For influenza codes, the PPV was 100% according to both reviewers and references, and between 63% and 90% depending on reviewer and reference for pneumonia. The rVE consistently favored HD vs. SD against validated events.
Conclusion: Hospitalizations for pneumonia registered in the DNPR may benefit from subsequent validation, warranting further studies. HD influenza vaccination was associated with fewer validated events compared with SD.
Keywords: DANFLU-1; Danish National Patient Registry; High-dose influenza vaccine; ICD-10; INFLUENZA; Pneumonia; Positive predictive value.