| Summary: | <p><strong>Introduction</strong>:
Culture-negative (CN) prosthetic joint infections (PJIs) account for
approximately 10 % of all PJIs and present significant challenges for
clinicians. We aimed to explore the significance of CN PJIs within a large
prospective cohort study, comparing their characteristics and outcomes with
culture-positive (CP) cases.
<strong>Methods</strong>:
The Prosthetic joint Infection in Australia and New Zealand Observational
(PIANO) study is a prospective, multicentre observational cohort study
that was conducted at 27 hospitals between 2014 and 2017. We compared baseline
characteristics and outcomes of all patients with CN PJI from the PIANO
cohort with those of CP cases. We report on PJI diagnostic criteria in the CN cohort
and apply internationally recognized PJI diagnostic guidelines to determine
optimal CN PJI detection methods.
<strong>Results</strong>:
Of the 650 patients with 24-month outcome data available, 55 (8.5 %) were
CN and 595 were CP. Compared with the CP cohort, CN patients were more
likely to be female (32 (58.2 %) vs. 245 (41.2 %); <span class="inline-formula"><i>p</i></span> <span class="inline-formula">=</span> 0.016), involve
the shoulder joint (5 (9.1 %) vs. 16 (2.7 %); <span class="inline-formula"><i>p</i></span> <span class="inline-formula">=</span> 0.026), and have a
lower mean C-reactive protein (142 mg L<span class="inline-formula"><sup>−1</sup></span> vs. 187 mg L<span class="inline-formula"><sup>−1</sup></span>; <span class="inline-formula"><i>p</i></span> <span class="inline-formula">=</span> 0.016). Overall,
outcomes were superior in CN patients, with culture negativity an
independent predictor of treatment success at 24 months (adjusted odds ratio, aOR, of 3.78 and 95 %CI of
1.65–8.67). Suboptimal diagnostic sampling was common in both cohorts,
with CN PJI case detection enhanced using the Infectious Diseases Society of
America PJI diagnostic guidelines.
<strong>Conclusions</strong>:
Current PJI diagnostic guidelines vary substantially in their ability to
detect CN PJI, with comprehensive diagnostic sampling necessary to achieve
diagnostic certainty. Definitive surgical management strategies should be
determined by careful assessment of infection type, rather than by culture
status alone.</p>
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