LEP was not an independent predictor of 7-day pneumonia (aOR 2.77, CI 0.57-13.51) after knee arthroplasty

Description #

After covariate adjustment, the association between limited English proficiency (LEP) and 7-day postoperative pneumonia was no longer statistically significant: the adjusted odds ratio was 2.77 with a wide 95% CI of 0.57–13.51 that crosses 1 (Figure 2). Although the crude rate was significantly higher for LEP patients (1.3% vs 0.3%, p = 0.02), pneumonia was not among the complications the authors reported as remaining significant on multivariable analysis (only 30-day DVT and 30-day VTE were).

"7-day Pneumonia 2.77 (0.57,13.51)" (Nguyen, 2023, Fig. 2, p. 579)

"Multivariable logistic regressions adjusted for age, gender, BMI, ASA physical status, smoking status, and length of hospitalisation found that patients with LEP had higher rates of 30‐day postoperative DVT (aOR: 2.84, CI:1.19–6.79, p = 0.02) and 30‐day VTE (aOR: 2.10 CI:1.06–4.12, p = 0.03) when compared to their EP counterparts (Figure 2)." (Nguyen, 2023, p. 577)

Methods Context #

What? #ⓘ

The observable: the covariate-adjusted odds of 7-day postoperative pneumonia for LEP relative to EP patients.

"Multivariable logistic regression modelling was used to calculate adjusted odds ratios of having a postoperative complication." (Nguyen, 2023, p. 577)

How? #ⓘ

Multivariable logistic regression with an a-priori covariate set (age, gender, BMI, ASA class, smoking, length of stay); race/ethnicity excluded owing to collinearity with English proficiency.

"Calculated odds ratios were adjusted for covariates chosen a prior based on prior arthroplasty literature, including age, patient‐reported gender, BMI, ASA physical status, smoking status, and length of hospitalisation (Gronbeck et al., 2019; Ko et al., 2021)." (Nguyen, 2023, p. 577)

Who? #ⓘ

3450 elective TKA cases at a single academic medical centre (2013–2021), 9.2% (316) with LEP; postoperative pneumonia was a rare event.

"A total of 3450 TKA cases were performed between January 2013 and December 2021. 9.2% (316) of the patients were classified as having LEP." (Nguyen, 2023, p. 577)

Other Notes #

The very wide CI (0.57–13.51) reflects the small number of pneumonia events; this adjusted null contradicts the crude pneumonia association and is captured as contradicting evidence on the pneumonia claim.

Caveats #

• Rare complication events yielded imprecise adjusted odds ratios with wide confidence intervals Postoperative complications were rare events (crude rates mostly 0.1%–3.8%) in a cohort with only 316 LEP patients, so the adjusted odds-ratio estimates are imprecise. This is visible in the wide confidence intervals — 30-day DVT aOR 2.84 (1.19–6.79) and, most strikingly, 7-day pneumonia aOR 2.77 (0.57–13.51), whose interval spans more than 20-fold and crosses 1. The significant thromboembolic estimates should be treated as directionally suggestive but imprecise, and the point estimates as fragile.
• Race and ethnicity excluded from adjustment due to collinearity with LEP, leaving residual confounding Race and ethnicity were dropped from the multivariable models because they were highly collinear with English-proficiency status (LEP patients were predominantly AAPI and Hispanic/Latinx). As a result, the adjusted odds ratios cannot separate the effect of language proficiency from that of race/ethnicity, and residual confounding by these correlated social factors remains. The "independent" adjusted association between LEP and thromboembolic complications should therefore be read as language proficiency inseparable from its correlated racial/ethnic context, not as a language effect net of race.