I am grateful for the important contribution made by Dr Trovato and colleagues to the interpretation of our article1 regarding the benefits of ultrasound guidance. We used detailed automated health insurance records to assemble large populations of patients undergoing thoracentesis and paracentesis. Most procedures were not accompanied by ultrasound guidance, although ultrasound guidance was associated with reduced risks of pneumothorax and bleeding complications. Health insurance claims facilitate large populations and enhance precision of effect estimates, but often do not provide a complete clinical picture of all relevant factors. Dr Trovato and colleagues alert us to improved visualization offered by certain transducers. Our study measured average effects of ultrasound guidance as it is used in current clinical practice. We did not have access to certain details regarding transducer type, nor could we evaluate sonographic technique, training, and other aspects of the procedures. We appreciate the potential importance that these factors might have in further improving patient safety.