Detection of middle-ear fluid in children with spectral gradient acoustic reflectometry: a screening tool for nurses?

Objective. To evaluate the validity of spectral gradient acoustic reflectometry (SG-AR) in the hands of nurses in screening children for middle-ear fluid (MEF). Design. Prospective, blinded study. Setting. A satellite study within the Finnish Otitis Media Vaccine Trial in primary care in 1995 - 99. Patients. Some 739 ear examinations among a cohort of 271 children under the age of 2 years during different healthcare contacts ( acute sick visits, check-up visits after otitis media, and scheduled healthy control visits at 24 months of age). Main outcome measures. Specificity, sensitivity and positive and negative predictive values of SG-AR performed by nurses in detecting MEF using pneumatic otoscopy by trained physicians as a reference. Results. SG-AR was successful in 585 (79%) ears. None of the cut-off points assessed resulted in both excellent sensitivity and specificity. Nevertheless, at the sick visits, positive predictive values at 50 and 60 degrees were as high as 94% and 89%, respectively. However, negative predictive value for the cut-off point of 100 degrees was considerably lower, at 75%. At the non-acute visits, negative predictive values were excellent. Conclusion. SG-AR is a useful device for nurses in screening MEF among children. It detects ears with both very high and very low probability of MEF and is especially effective in detecting MEF during sick visits and in ruling out MEF among non-acute patients. We recommend the use of the SG-AR cut-off point of 60 degrees as a sign of MEF when screening sick children, and the cut-off point of 100 degrees as a sign of a healthy ear among non-symptomatic patients.