On the Analytic Characteristics of Commercial Acetaminophen Assays in the United States.

BACKGROUND: The management of patients with acetaminophen (APAP) toxicity is largely informed by the blood concentration. We sought to assess the analytical characteristics of past and current commercial APAP assays in the United States. METHODS: We systematically reviewed the analytical characteristics of APAP assays cleared by the Food and Drug Administration's (FDA) 510(k) premarket notification process by searching the Clinical Laboratory Improvement Amendments (CLIA) database. We collected the following data where available: test principle, precision near 10 mg/L, precision near 150 mg/L, limits of detection, and limits of quantitation. RESULTS: For all assays, absolute analytical precision decreased as analyte concentration increased. Near [APAP] = 10 mg/L, the most precise assays had a standard deviation (SD) of 0.2 mg/L or coefficient of variation (CV) of 1% and the least precise assays had a SD of 1.8 mg/L or a CV of 10%. Near [APAP] = 150 mg/L, the most precise assay had a SD of 1.4 mg/L or CV of 0.9% and the least precise assays had a SD of 7.4 mg/L or a CV of 4.9%. CONCLUSIONS: Commercially available APAP assays had good analytical precision with improvement over time. The failure of some manufacturers to validate precision near treatment thresholds is concerning. Newer APAP assays can measure a wider range of [APAP], which likely improves the risk stratification of overdose patients but also carries a risk of overdiagnosis when minuscule quantities are detected.

Deepening Trochleoplasty With a Thick Osteochondral Flap for Patellar Instability: Clinical and Functional Outcomes at a Mean 6-Year Follow-up.

BACKGROUND: In patients with patellar instability and severe trochlear dysplasia, trochleoplasty has become increasingly used as part of its surgical management. HYPOTHESIS: Deepening trochleoplasty for severe dysplasia in patellofemoral instability improves function and increases sports participation. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Between 1995 and 2010, deepening trochleoplasty with a thick flap was performed in 90 patients (107 knees) with severe trochlear dysplasia. Data were collected prospectively preoperatively, at 6 weeks, and at 1-year follow-up. The patients were surveyed retrospectively to determine the clinical and functional outcomes including sports and exercise participation at a minimum of 2 years, with complete data available in 92%. RESULTS: The average follow-up was 6 years (range, 2-19 years). The median Kujala score was 63 (interquartile range [IQR], 47-75) preoperatively, rising to 79 (IQR, 68-91) at 1-year follow-up and 84 (IQR, 73-92) at final follow-up (P < .05). Seventy-two percent were satisfied with their knee function at 1-year follow-up, rising to 83% at final follow-up (P < .0001). Sports and exercise participation increased from 36 patients (40%) preoperatively to 60 (67%) at final follow-up. The number of patients involved in competitions increased slightly from 10 (11%) to 11 (12%). Of those sports that involved twisting (e.g., soccer, cricket, badminton), the number of patients participating increased from 16 (18%) to 22 (24%), whereas in nontwisting sports (e.g., running, swimming, cycling), it increased from 24 (27%) to 47 (52%), of whom 12 (16%) used walking as exercise. Two patients who had undergone medial patellofemoral ligament (MPFL) reconstruction as the index operation needed the MPFL revised, and a further 8 patients needed MPFL reconstruction subsequently for instability symptoms and a mediolateral glide in extension of more than 2 quadrants' displacement. At final follow-up, no patient had mechanical patellofemoral instability. CONCLUSION: Deepening trochleoplasty with a thick flap improves clinical and functional outcomes for patients with symptomatic patellar instability with severe trochlear dysplasia. These results improve over time and beyond 1-year clinical follow-up. However, trochleoplasty does not lead to a significant improvement in sports participation at a competitive level. It does improve patient participation in sports and exercise, principally in nontwisting sports activities.