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Osteomyelitis and the Tarnished Gold Standard
Editorial
Osteomyelitis and the Tarnished Gold Standard
All foot and ankle surgeons are aware of this, but it bears repeating that the treatment of osteomyelitis is neither innocuous nor inexpensive. Just this past summer, one of my diabetic patients who had been diagnosed with osteomyelitis of the metatarsus developed acute renal failure during his third week of intravenous vancomycin therapy following definitive debridement of the bone to what I felt was a clean margin. His renal shutdown required cessation of the antibiotic, admission to the intensive care unit, and 4 weeks of supportive therapy before his serum creatinine returned to normal. Although he experienced a favorable recovery, many patients do not fare so well. Before embarking on a course of treatment with such dire risks, I had relied on what is usually considered the gold standard –bone biopsy –for the diagnosis. For any disease, the ideal diagnostic test is 100% sensitive (positive each and every time the disease is present, and only when the disease is present –no false
negative results) and 100% specific (negative each and every time the disease is absent, only when the disease is absent –no false positive results). Even when this is true, the baseline prevalence of the condition of interest will influence the predictive value of a diagnostic test. Low prevalence makes a highly sensitive test more likely to return a false positive and a highly specific test subject to false negatives (like osteomyelitis in the infected diabetic foot). In fact, the reliability of bone biopsy has been brought into question by a report published in The Journal of Foot & Ankle SurgeryÒ that described the results of having 4 musculoskeletal pathologists review the same bone biopsy slides from 39 cases of diabetic foot infection. The results showed 33.33% agreement (k ¼ 0.31), wherein the goal of the surgery was debridement and identification of osteomyelitis if it was truly present (1). So it seems that, when it comes to the diagnosis of osteomyelitis, we may be dealing with a tarnished gold standard. Traditionally, I based the diagnosis of osteomyelitis on a number of variables, including the clinical history and the appearance of the wound, radiographs and, not infrequently, magnetic resonance images, as well as microbiological testing (culture and sensitivity) of the debrided bone; however, it was bone biopsy that served as the de facto gold standard diagnostic test for osteomyelitis in the foot. Now, however, it seems more important than ever to temper the biopsy result with the surgical appearance and microbiology of the bone in question because I can recall cases where the diagnosis of osteomyelitis seemed apparent until the results of the biopsy refuted the diagnosis. In other cases, the results were just the opposite: I had strong suspicion that osteomyelitis was not present, and the biopsy was interpreted as representative of osteomyelitis. So, when it comes to making a diagnosis of osteomyelitis, I think that we need to rely a great deal on our past experience, and keep in mind the results of the aforementioned publication (1) when we biopsy suspicious bone. Thereafter, we need to follow the clinical course and adjust therapy based on our patients’ progress. And while bone biopsy is likely to remain the gold standard in the near term, further clinical investigation is required before we can formulate a better understanding of the precise role that it plays in the diagnosis of osteomyelitis in the diabetic foot. D. Scot Malay, DPM, MSCE, FACFAS Editor The Journal of Foot & Ankle SurgeryÒ Reference 1. Meyr AJ, Singh S, Zhang X, Khilko N, Mukherjee A, Sheridan MJ, Khurana JS. Statistical reliability of bone biopsy for the diagnosis of diabetic foot osteomyelitis. J Foot Ankle Surg 50:663–667, 2011.
1067-2516/$ - see front matter Ó 2013 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2012.11.008
Osteomyelitis and the Tarnished Gold Standard
All foot and ankle surgeons are aware of this, but it bears repeating that the treatment of osteomyelitis is neither innocuous nor inexpensive. Just this past summer, one of my diabetic patients who had been diagnosed with osteomyelitis of the metatarsus developed acute renal failure during his third week of intravenous vancomycin therapy following definitive debridement of the bone to what I felt was a clean margin. His renal shutdown required cessation of the antibiotic, admission to the intensive care unit, and 4 weeks of supportive therapy before his serum creatinine returned to normal. Although he experienced a favorable recovery, many patients do not fare so well. Before embarking on a course of treatment with such dire risks, I had relied on what is usually considered the gold standard –bone biopsy –for the diagnosis. For any disease, the ideal diagnostic test is 100% sensitive (positive each and every time the disease is present, and only when the disease is present –no false
negative results) and 100% specific (negative each and every time the disease is absent, only when the disease is absent –no false positive results). Even when this is true, the baseline prevalence of the condition of interest will influence the predictive value of a diagnostic test. Low prevalence makes a highly sensitive test more likely to return a false positive and a highly specific test subject to false negatives (like osteomyelitis in the infected diabetic foot). In fact, the reliability of bone biopsy has been brought into question by a report published in The Journal of Foot & Ankle SurgeryÒ that described the results of having 4 musculoskeletal pathologists review the same bone biopsy slides from 39 cases of diabetic foot infection. The results showed 33.33% agreement (k ¼ 0.31), wherein the goal of the surgery was debridement and identification of osteomyelitis if it was truly present (1). So it seems that, when it comes to the diagnosis of osteomyelitis, we may be dealing with a tarnished gold standard. Traditionally, I based the diagnosis of osteomyelitis on a number of variables, including the clinical history and the appearance of the wound, radiographs and, not infrequently, magnetic resonance images, as well as microbiological testing (culture and sensitivity) of the debrided bone; however, it was bone biopsy that served as the de facto gold standard diagnostic test for osteomyelitis in the foot. Now, however, it seems more important than ever to temper the biopsy result with the surgical appearance and microbiology of the bone in question because I can recall cases where the diagnosis of osteomyelitis seemed apparent until the results of the biopsy refuted the diagnosis. In other cases, the results were just the opposite: I had strong suspicion that osteomyelitis was not present, and the biopsy was interpreted as representative of osteomyelitis. So, when it comes to making a diagnosis of osteomyelitis, I think that we need to rely a great deal on our past experience, and keep in mind the results of the aforementioned publication (1) when we biopsy suspicious bone. Thereafter, we need to follow the clinical course and adjust therapy based on our patients’ progress. And while bone biopsy is likely to remain the gold standard in the near term, further clinical investigation is required before we can formulate a better understanding of the precise role that it plays in the diagnosis of osteomyelitis in the diabetic foot. D. Scot Malay, DPM, MSCE, FACFAS Editor The Journal of Foot & Ankle SurgeryÒ Reference 1. Meyr AJ, Singh S, Zhang X, Khilko N, Mukherjee A, Sheridan MJ, Khurana JS. Statistical reliability of bone biopsy for the diagnosis of diabetic foot osteomyelitis. J Foot Ankle Surg 50:663–667, 2011.
1067-2516/$ - see front matter Ó 2013 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2012.11.008