Cohort studyindependent cross-checkabstract checked★ key study I-ORG-115 in-depth review

Infections after spleen removal in Denmark

Risk for hospital contact with infection in patients with splenectomy: a population-based cohort study.

Overview

Thomsen RW et al.. Ann Intern Med 2009 · PMID 19841456 · DOI 10.7326/0003-4819-151-8-200910200-00008

People without a spleen had more serious infections for years after surgery, although part of the extra risk came from their underlying disease.

Does the study support the specific claim? Yes · Methodological quality: high

Original publication

Plain-language summary

Study explained simply

What did the researchers want to find out?: Measure long-term infection risk after splenectomy
How was the study done?: National cohort with three comparison groups
How many people, animals or samples were studied?: 3812 Danish patients
What was actually found?: Infection risk raised early and still 2.5-fold after one year
How large was the observed effect?: HR 2.5 (>1 year) vs population
What do the results mean in everyday life?: People without a spleen need vaccinations and fast care for fever
What are the study's limitations?: Possible surveillance bias
What does it say about Elawady's specific claim?: Supports the claim
Do the results apply to Germany and Europe?: Directly applicable
What can explicitly not be concluded from this study?: Cannot fully separate surgery from disease effects

Scientific in-depth review

1. Full reference

Authors: Thomsen RW et al.
Journal: Ann Intern Med
Year: 2009
Identifier: PMID 19841456 DOI 10.7326/0003-4819-151-8-200910200-00008
Verification: verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: Non-commercial support (PubMed).

2. Research question

Magnitude and duration of risk for hospital contact with infection after splenectomy.

3. Study design and population

Study design: Cohort study – Population-based cohort study with three matched comparison cohorts
Population: All 3812 persons splenectomised in Denmark 1996-2005
Country: Denmark
Period: 1996-2005 with follow-up
Sample size: 3812 splenectomised plus matched general population, appendectomised and indication-matched unsplenectomised cohorts
Inclusion and exclusion criteria: All splenectomies in national registries

4. Methods and endpoints

Exposure / intervention: Splenectomy
Comparator: General population; appendectomised patients; patients with the same indications without splenectomy
Endpoints: Hospital contact with infection, pneumonia, bacteraemia
Statistical methods: Adjusted OR and HR by follow-up period

5. Actual results

Results: Infection within 90 days: 10.2% vs 0.6% (general population; adjusted OR 18.1, 95% CI 14.8-22.1) and vs 4.2% (appendectomised; OR 2.4, 2.1-2.8). HR vs population 4.6 (3.8-5.5) at 91-365 days and 2.5 (2.2-2.8) after 365 days. Similar for pneumonia, higher for bacteraemia. Vs indication-matched patients: 90-day OR 1.7 (1.5-2.1), HR 1.5 (1.2-1.8) at 91-365 days and 1.2 (1.1-1.4) beyond 365 days. Highest relative risks after splenectomy for haematological disorders.
Absolute risks: 90-day infection 10.2% vs 0.6% (population).
Authors' conclusion: Splenectomy is associated with increased long-term risk for infections involving hospital contact.

6. Strengths

Complete national population
Three comparison cohorts incl. indication-matched

7. Weaknesses

Surveillance bias possible (authors)
Hospital-contact outcomes only

8. Risk of bias

Orienting tool: ROBINS-E
Type of assessment: simplified assessment (abstract only)
Full formal assessment: no
Overall risk of bias: some concerns
Rationale: Confounding by indication partly addressed with indication-matched comparison.

9. Assessment of the statistical interpretation

CIs approximately log-symmetric (stats/C-ORG-12_13_splenectomy.py). The excess shrinks markedly when compared with patients who have the same underlying disease, showing that part of the risk is due to the disease.

10. Relevance to the specific claim

Quantifies lasting infection risk after splenectomy.

11. Independent contrary findings

Indication-matched comparison shows a smaller late excess (HR 1.2).

12. Transferability to Germany and Europe

Danish; directly applicable.

13. Overall methodological judgement

Supports the claim that infection risk persists for years after splenectomy, though the late excess attributable to the operation itself is modest.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	high
Risk of bias	some concerns
Precision of results	high
Directness	direct
Reproducibility	replicated
Consistency with the overall evidence	consistent
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

14. Open questions

Effect of modern vaccination programmes.