Early Versus Late Culture Growth of Propionibacterium acnes in Revision Shoulder Arthroplasty
Bibliographic record
Abstract
BACKGROUND: Propionibacterium acnes is recognized as a pathogenic organism associated with periprosthetic joint infection following shoulder arthroplasty. The goal of our study was to determine the relationship between the time to P. acnes growth in culture and the likelihood of a culture result being a true positive versus a false positive based on the proportion of positive cultures and other perioperative findings in cases of revision shoulder arthroplasty. METHODS: We retrospectively reviewed forty-six cases with P. acnes-positive cultures among patients who underwent revision shoulder arthroplasty between May 2010 and October 2014. Tissue and fluid was cultured anaerobically for a mean (and standard deviation) of 13.1 ± 3 days. Cases were categorized into one of two groups for analysis: probable true positive or probable contaminant (false-positive) on the basis of culture results and perioperative findings. RESULTS: The time to P. acnes culture growth was significantly shorter (p = 0.002) in the probable true-positive culture group compared with the probable contaminant group (median of five days [interquartile range, four to seven days]) compared with nine days [interquartile range, six to twelve days]). Among the thirty-seven cases in the probable true-positive group, no culture result turned positive after eleven days, whereas in the probable contaminant group, cultures turned positive after this time point in 44% (four of nine) of the cases. There were also significantly fewer days to P. acnes culture growth among cases with a higher number of positive cultures (p = 0.001) and a higher proportion of positive cultures (p < 0.001), regardless of group classification. CONCLUSIONS: P. acnes is the most commonly identified organism following revision shoulder arthroplasty. The proportion of positive cultures and the timing of culture growth may help to distinguish a true-positive from a false-positive culture result. LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".