Infection is a leading indication for revision
arthroplasty. Established criteria used to diagnose prosthetic joint infection
(PJI) include a range of laboratory tests. Leucocyte esterase (LE)
is widely used on a colorimetric reagent strip for the diagnosis
of urinary tract infections. This inexpensive test may be used for
the diagnosis or exclusion of PJI. Aspirates from 30 total hip arthroplasties
(THAs) and 79 knee arthroplasties (KA) were analysed for LE activity. Semi-quantitative
reagent strip readings of 15, 70, 125 and 500 white blood cells
(WBC) were validated against a manual synovial white cell count
(WCC). A receiver operating characteristic (ROC) curve was constructed
to determine the optimal cut-off point for the semi-quantitative
results. Based on established criteria, six THAs and 15 KAs were
classified as infected. The optimal cut-off point for the diagnosis
of PJI was 97 WBC. The closest semi-quantitative reading for a positive
result was 125 WBC, achieving a sensitivity of 81% and a specificity
of 93%. The positive and negative predictive values of the LE test
strip were 74% and 95% respectively. The LE reagent strip had a high specificity and negative predictive
value. A negative result may exclude PJI and negate the need for
further diagnostic tests. Cite this article:
We report a systematic review and meta-analysis
of the peer-reviewed literature focusing on metal sensitivity testing
in patients undergoing total joint replacement (TJR). Our purpose
was to assess the risk of developing metal hypersensitivity post-operatively
and its relationship with outcome and to investigate the advantages
of performing hypersensitivity testing. We undertook a comprehensive search of the citations quoted in
PubMed and EMBASE: 22 articles (comprising 3634 patients) met the
inclusion criteria. The frequency of positive tests increased after
TJR, especially in patients with implant failure or a metal-on-metal
coupling. The probability of developing a metal allergy was higher
post-operatively (odds ratio (OR) 1.52 (95% confidence interval
(CI) 1.06 to 2.31)), and the risk was further increased when failed
implants were compared with stable TJRs (OR 2.76 (95% CI 1.14 to
6.70)). Hypersensitivity testing was not able to discriminate between
stable and failed TJRs, as its predictive value was not statistically
proven. However, it is generally thought that hypersensitivity testing
should be performed in patients with a history of metal allergy
and in failed TJRs, especially with metal-on-metal implants and
when the cause of the loosening is doubtful.
