Sensitivity, specificity and predictive values of anterior chamber tap in cases of bacterial endophthalmitis

Abstract

BackgroundTo assess the sensitivity, specificity, positive predictive value and negative predictive value of anterior chamber tap for the diagnosis of bacterial endophthalmitis on a population with high prevalence.MethodsRetrospective, single centre, case series study. We reviewed all medical records with clinical diagnosis of bacterial endophthalmitis in our hospital from January 1st, 2000 to December 31st 2014. From each record, we documented general demographic data, best corrected visual acuity and vitreous and aqueous tap microbiological results. All cases were further divided according to the endophthalmitis aetiology to perform individual calculations of sensitivity, specificity, positive predictive value, negative predictive value, accuracy and prevalence. We used the results of the vitreous tap as the gold standard for diagnosis of bacterial endophthalmitis. We excluded those records in which the aqueous and vitreous samples were not taken simultaneously or had an incomplete microbiological report. Significance were assessed with chi squared statistics, with an alpha value of 0.05 for statistical significance.ResultsA total of 190 cases fulfilled the inclusion/exclusion criteria. Positive culture rate from vitreous samples was 64.74%. Positive culture rate from aqueous sample was 32.11%. Bacteria isolated from aqueous samples matched those isolated from vitreous samples 78.68% of the time. The overall sensitivity was 38.21%, specificity: 75.51%, positive predictive value: 79.66%, negative predictive value: 32.74% (p = 0.08). Subgroup analysis showed that anterior chamber taps in cases of post-surgical endophthalmitis had a moderate to low sensitivity (37.73%), high specificity (93%) and high positive predictive value (95%) (p < 0.04).ConclusionThe sensitivity and specificity of anterior chamber tap are low and should not be used for critical therapeutic decisions in patients with suspected bacterial endophthalmitis. In cases of post-surgical endophthalmitis, the result of an anterior chamber tap could be used for therapeutic guidance, but only in conjunction with clinical presentation and in the absence of a better method for diagnosis.

Characterization of postoperative “fibrin web” formation after canine cataract surgery

“…An aqueous humor sample was collected from 3 of these eyes, but the cultures did not produce any bacterial growth, thus in all likelihood our affected patients were mostly sterile endophthalmitis cases, which has been reported 42 . However, since vitreal samples nor histopathology was obtained, it is not possible to be definitive in this conclusion 43,44 . One report involving human pediatric patients demonstrated that fibrin formation does not appear to be caused by bacterial contamination, 22 further supporting the assertion that intracameral FW formation, as described in the present study, is distinct from infectious endophthalmitis, but rather, may be considered by some ophthalmologists as a manifestation of mild TASS.…”

Using the West Midlands CONCERT to characterise regional incidence of acute-onset post cataract surgery endophthalmitis

“…Conversely, in four cases a positive vitreous culture was accompanied by a negative aqueous culture from the same patient, suggesting that aqueous culture has poorer sensitivity. These findings are in keeping with both studies in animal models [ 22 ] and those previously reported in clinical studies showing aqueous tap culture-positive rates in 20–37.7% of clinically diagnosed endophthalmitis cases compared to 48.8–74% of vitreous samples [ 23 , 24 ]. Despite overall greater sensitivity of vitreous cultures, some studies report the occasional aqueous sample culture showing pathogenic microorganism growth (rather than contaminant) where a corresponding vitreous sample culture is negative [ 25 , 26 ].…”

The Impact of Primary Treatment on Post-Traumatic Endophthalmitis in Children with Open Globe Injuries: A Study in China

“…Endophtalmitis is a potential blinding complication characterized by the inflammation, colonization and irreversible destruction by an infectious agent, which is uncommon, but one of the most severe complications after OGIs [21]. In our study, the incidence of PTE after OGIs was 21.4% compared to 3.6% to 54.16% reported by other studies from different institutions [6,7].…”