<p><strong>BACKGROUND: </strong>A "champagne tap" is a lumbar puncture with no cerebrospinal fluid (CSF) red blood cells (RBCs). Clinicians disagree whether the absence of CSF white blood cells (WBCs) is also required.</p>

<p><strong>AIMS: </strong>As supervising providers frequently reward trainees after a champagne tap, we investigated how varying the definition impacted the frequency of trainee accolades.</p>

<p><strong>MATERIALS &amp; METHODS: </strong>We performed a secondary analysis of a retrospective cross-sectional study of infants ≤60&nbsp;days of age who had a CSF culture performed in the emergency department (ED) at one of 20 centers participating in a Pediatric Emergency Medicine Collaborative Research Committee (PEM CRC) endorsed study. Our primary outcomes were a champagne tap defined by either a CSF RBC count of 0&nbsp;cells/mm regardless of CSF WBC count or both CSF RBC and WBC counts of 0&nbsp;cells/mm .</p>

<p><strong>RESULTS: </strong>Of the 23,618 eligible encounters, 20,358 (86.2%) had both a CSF RBC and WBC count obtained. Overall, 3,147 (13.3%) had a CSF RBC count of 0&nbsp;cells/mm and 377 (1.6%) had both CSF WBC and RBC counts of 0&nbsp;cells/mm (relative rate 8.35, 95% confidence interval 7.51 to 9.27).</p>

<p><strong>CONCLUSIONS: </strong>In infants, a lumbar puncture with a CSF RBC count of 0&nbsp;cells/mm regardless of the CSF WBC count occurred eight-times more frequently than one with both CSF WBC and RBC counts of 0&nbsp;cells/mm . A broader champagne tap definition would allow more frequent recognition of procedural success, with the potential to foster a supportive community during medical training, potentially protecting against burnout.</p>

<p><strong>BACKGROUND: </strong>The ability of the decades-old Boston and Philadelphia criteria to accurately identify infants at low risk for serious bacterial infections has not been recently reevaluated.</p>

<p><strong>METHODS: </strong>We assembled a multicenter cohort of infants 29 to 60 days of age who had cerebrospinal fluid (CSF) and blood cultures obtained. We report the performance of the modified Boston criteria (peripheral white blood cell count [WBC] ≥20 000 cells per mm, CSF WBC ≥10 cells per mm, and urinalysis with &gt;10 WBC per high-power field or positive urine dip result) and modified Philadelphia criteria (peripheral WBC ≥15 000 cells per mm, CSF WBC ≥8 cells per mm, positive CSF Gram-stain result, and urinalysis with &gt;10 WBC per high-power field or positive urine dip result) for the identification of invasive bacterial infections (IBIs). We defined IBI as bacterial meningitis (growth of pathogenic bacteria from CSF culture) or bacteremia (growth from blood culture).</p>

<p><strong>RESULTS: </strong>We applied the modified Boston criteria to 8344 infants and the modified Philadelphia criteria to 8131 infants. The modified Boston criteria identified 133 of the 212 infants with IBI (sensitivity 62.7% [95% confidence interval (CI) 55.9% to 69.3%] and specificity 59.2% [95% CI 58.1% to 60.2%]), and the modified Philadelphia criteria identified 157 of the 219 infants with IBI (sensitivity 71.7% [95% CI 65.2% to 77.6%] and specificity 46.1% [95% CI 45.0% to 47.2%]). The modified Boston and Philadelphia criteria misclassified 17 of 53 (32.1%) and 13 of 56 (23.3%) infants with bacterial meningitis, respectively.</p>

<p><strong>CONCLUSIONS: </strong>The modified Boston and Philadelphia criteria misclassified a substantial number of infants 29 to 60 days old with IBI, including those with bacterial meningitis.</p>