|Year : 2016 | Volume
| Issue : 2 | Page : 64-70
Consistency of microbiological and pathological tests between infected bone and surrounding deep soft tissues in diabetic foot osteomyelitis: study protocol for a single-center, self-controlled, open-label trial
Jun Xu, Peng-hua Wang, Xue-mei Li, Shu-hong Feng, Min Ding, Xi-wen Li, Wei-jie Yao, Zi-xi Zhao
Key Laboratory of Hormones and Development (Ministry of Health), Tianjin Key Laboratory of Metabolic Diseases, Tianjin Metabolic Diseases Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China
|Date of Web Publication||31-May-2016|
Key Laboratory of Hormones and Development (Ministry of Health), Tianjin Key Laboratory of Metabolic Diseases, Tianjin Metabolic Diseases Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin
Source of Support: None, Conflict of Interest: None
Background: Diabetic foot osteomyelitis is a mixed bone infection, and early detection and treatment can avoid unnecessary amputation and improve patient survival. However, determining an accurate diagnosis is a difficult and commonly encountered challenge. Most patients fail to exhibit any overt symptoms or hematological characteristics despite the presence of a severe limb infection. The most commonly used clinical standard for diagnosis is histological and microbiological examination of the bone tissue. However, such examinations are not feasible in all patients suspected to have diabetic foot osteomyelitis, and many affected patients have an insufficient understanding of the need to repeatedly collect bone samples and thus exhibit poor compliance. Further, the proper use of antibiotics in the treatment of diabetic foot osteomyelitis is severely hampered by the difficulty of diagnosis. Considering that patients often develop soft tissue infection followed by bone infection, we assume that the histological and microbiological findings of bone tissue are consistent with those of the deep soft tissue around the bone infection. In this study, we will explore whether deep soft tissue specimens are an alternative to bone tissue specimens in histological and microbiological tests for the clinical diagnosis of diabetic foot osteomyelitis.
Methods/Design: A prospective, single-center, self-controlled, open-label trial will be completed at Tianjin Metabolic Diseases Hospital of Tianjin Medical University in China. A total of 200 patients with diabetic foot osteomyelitis, aged 18 to 80 years, of both sexes, and admitted as outpatients from 1 April 2015 to 30 June 2016 will be recruited and subjected to histological and microbiological examinations of infected bone and surrounding deep soft tissue. The primary outcome will be the sensitivity and specificity of microbial cultures of infected bone and surrounding deep soft tissue at admission for diabetic foot osteomyelitis. The secondary outcomes will be blood biochemical indices, X-ray characteristics of the affected foot, and the blood supply of the affected lower limb. Findings from the microbial cultures of bone and deep soft tissue will be used to calculate the positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for the diagnosis of diabetic foot osteomyelitis. We will therefore be able to verify whether the histological and microbiological tests exhibit consistent results between infected bone and surrounding deep soft tissue.
Discussion: Findings from this trial will provide new insight into the early diagnosis and proper use of antibiotics based on repeated diagnoses in patients with diabetic foot osteomyelitis.
Trial registration: This protocol was registered at Chinese Clinical Trial Registry (identifier: ChiCTR-DCC-15006104) on 12 March 2015.
Ethics: Written approval for this trial was obtained from the Ethics Committee of the Tianjin Metabolic Diseases Hospital, Tianjin Medical University of China (approval No. DXBXYhMEC2015-7). This study will be performed in accordance with the guidelines of the Declaration of Helsinki, formulated by the World Medical Association.
Informed consent: Written informed consent will be obtained from each participant.
Keywords: clinical trial; diabetic foot osteomyelitis; bone; soft tissue; microbial cultures; pathological examination; correlation; sensitivity; specificity; self-controlled open-label trial
|How to cite this article:|
Xu J, Wang Ph, Li Xm, Feng Sh, Ding M, Li Xw, Yao Wj, Zhao Zx. Consistency of microbiological and pathological tests between infected bone and surrounding deep soft tissues in diabetic foot osteomyelitis: study protocol for a single-center, self-controlled, open-label trial. Clin Trials Orthop Disord 2016;1:64-70
|How to cite this URL:|
Xu J, Wang Ph, Li Xm, Feng Sh, Ding M, Li Xw, Yao Wj, Zhao Zx. Consistency of microbiological and pathological tests between infected bone and surrounding deep soft tissues in diabetic foot osteomyelitis: study protocol for a single-center, self-controlled, open-label trial. Clin Trials Orthop Disord [serial online] 2016 [cited 2020 Apr 2];1:64-70. Available from: http://www.clinicalto.com/text.asp?2016/1/2/64/183004
| Background|| |
Osteomyelitis of the foot in patients with diabetes often develops owing to a foot ulcer or infection secondary to neuropathy and ischemia (Vuorisalo et al., 2009). Patients with diabetes who develop ischemia due to lower limb arteriosclerosis-induced occlusion are at high risk for foot ulcers. Diabetic foot ulcers that become infected trigger severe infections of the bone and deep soft tissues (Haji et al., 2014; Dalla Paola et al., 2015). As previously reported, better control of multiresistant bacteria is important for improving the prognosis of diabetic foot ulcers ([Table 1]) (Ding et al., 2012; Guo et al., 2012; Ji et al., 2014; Zhang et al., 2014).
Early diagnosis of diabetic foot osteomyelitis can avert unnecessary amputation and increase the patient's survival (Babamahmoodi et al., 2015; Notopoulos et al., 2015; Ueki et al., 2015). Diabetic foot ulcers that are likely to develop into foot infections and rapidly deteriorate often result in osteomyelitis, eventually leading to gangrene of the foot (Wang, 2012). Unfortunately, patients with mixed infections often have no signs of infection or no specific hematological characteristics despite the presence of a severe limb infection (Faglia et al., 2016; Snyder et al., 2016).
As previously reported (Lipsky et al., 2006), histological and microbiological examinations of bone tissue are the gold standard for diagnosing diabetic foot osteomyelitis. Our experience has shown that patients with diabetic foot osteomyelitis often develop infections of the surrounding deep soft tissue. Thus, we hypothesize that histological and microbiological tests of bone tissue and deep soft tissue will provide consistent results. This prospective, single-center, self-controlled, open trial is designed to explore whether deep soft tissue specimens are an alternative to bone tissue specimens when performing histological and microbiological tests to clinically diagnose diabetic foot osteomyelitis. Findings from our study will provide new insight into the early diagnosis and treatment of diabetic foot osteomyelitis.
| Methods/Design|| |
This prospective, single-center, self-controlled, open trial will be completed at Tianjin Metabolic Diseases Hospital of Tianjin Medical University in China. A total of 200 patients with diabetic foot osteomyelitis admitted to the outpatient clinic of Tianjin Metabolic Diseases Hospital will be recruited and subjected to histological and microbiological examinations of infected bone and surrounding deep soft tissue ([Figure 1]).
Patients who meet all of the following will be eligible for this trial.
- Meet the diagnostic criteria for diabetic foot osteomyelitis recommended by the International Working Group on the Diabetic Foot in 2011
- Any site, severity, and duration of diabetic foot ulcer and any diabetic foot type
- 18 to 80 years of age
- Either sex
Patients with one of the criteria detailed below will be excluded from the trial.
- Severe limb ischemia, as defined by an ankle/brachial index of < 0.4 or a transcutaneous oxygen pressure of < 20 mmHg (1 mmHg = 0.133 kPa)
- Renal dysfunction, as defined by a serum creatinine level of > 98 μM in males and > 106 μM in females
- Liver dysfunction, as defined by an alanine aminotransferase level of > 100 U/L
- Stage IV heart function according to the New York Heart Association (Torvik et al., 1987)
Patients will be withdrawn from the study if any of the following occurs:
- If patients are unwilling to continuously participate in the trial and repeal their written informed consent, the patients will be withdrawn from the trial
- If severe adverse events occur, doctors will determine whether the patient should be withdrawn from the trial according to their experience
Sample size calculation
The sample size will be calculated using PASS 14.0 software (NCS, Kaysville, UT, USA). Generally, a microbial culture of bone tissue with > 95% sensitivity is defined as the gold standard for diabetic foot osteomyelitis. It is hypothesized that the microbial culture of bone tissue will achieve a sensitivity of up to 90%. If β ≤ 0.1, a power = 90%, and significance level α = 0.025 (bilateral), 582 patients will be needed for this trial. Allowing for 20% of the sample size to be lost, 699 patients will be required. However, because of the limited number of patients with diabetic foot osteomyelitis, only 200 patients will be enrolled in the trial.
Recruitment of patients with diabetic foot osteomyelitis through newspapers, hospital outlets, and the hospital website will be ongoing, according to the principle of voluntary participation. Interested patients can discuss the trial with their attending doctors and contact the principal investigator by telephone, e-mail, or letter. After written informed consent is given, the participants will be screened according to the inclusion and exclusion criteria.
Prior to antibiotic treatment, all enrolled patients will be subjected to adequate wound disinfection, surgical debridement, and collection of infected bone and surrounding necrotic tissues followed by pathogenic detection and pathological examination. The premise is a clear understanding of the types of pathogenic microorganisms and histological changes of infected bone and surrounding necrotic tissues in patients with diabetic foot osteomyelitis.
Soft tissue samples will be harvested on the day of opening the wound, but bone tissue samples cannot be collected in all participants (especially those with ischemic foot ulcers) until the affected toe is removed. Therefore, collection of bone tissue will slightly lag behind collection of soft tissue.
All participants will be examined by X-ray, blood biochemistry, and detection of the blood supply in their affected feet.
The primary outcomes will be the sensitivity and specificity of microbial cultures of infected bone and surrounding deep soft tissue at admission for diabetic foot osteomyelitis.
- The sensitivity, namely the true positive rate, is defined as the percentage of actual patients who are correctly diagnosed with diabetic foot osteomyelitis. A higher sensitivity refers to a higher rate of correct diagnosis.
- The specificity, namely the true negative rate, is defined as the percentage of disease-free patients who are correctly diagnosed with no diabetic foot osteomyelitis. A higher specificity refers to a higher rate of correct diagnosis.
- Microbiological detection: Bacterial type and drug resistance will be compared in microbial cultures of deep soft tissue and bone tissue. If the type of bacteria is consistent, then we can assume the bacteria responsible for the bone infection have originated from the surrounding soft tissue; i.e., the microbiological findings from the deep soft tissue represent those from bone tissue. If this is not true, then we must further analyze the cause of the bone infection.
- Pathological detection: Deep soft tissue and bone tissue will also be compared in a pathological examination. If their pathological findings are consistent and the same type of inflammatory cells has invaded each tissue, then the deep soft tissue can be used as a substitute for bone tissue in the pathological detection. If not, we must further analyze the cause of the bone infection.
- Blood biochemical test: Fasting blood samples will be taken on admission to determine the white blood cell count, absolute neutrophil count, erythrocyte sedimentation rate, C-reactive protein concentration, D-dimer concentration, hemoglobin concentration, hematocrit, albumin concentration, and serum iron concentration. Blood biochemical parameters exceeding the normal range indicate the presence of severe infection.
- X-ray observation of the affected foot will help detect osteoporosis, decalcification, osteomyelitis, bone and joint lesions, atherosclerosis, and soft tissue changes when gas gangrene occurs. Bone destruction, cortical discontinuity, and periosteal reaction shown by X-ray will indicate the presence of osteomyelitis; if not, the presence of osteomyelitis will not be excluded unless a plain X-ray film of the affected foot is reviewed 1 to 2 weeks later.
- Detection of the blood supply: (1) A transcutaneous partial pressure of oxygen of < 4.0 kPa indicates severe skin ischemia with refractory healing of local ulcers, and (2) an ankle-brachial index of < 0.8 indicates moderate disease and < 0.5 indicates severe disease. The ankle-brachial index of patients with intermittent claudication ranges from 0.35 to 0.90. Patients complaining of a rest-state pain whose ankle-brachial index is often < 0.4 are at risk of amputation. An ankle-brachial index of > 1.3 suggests vascular wall calcification and loss of vascular contractile function, which reflects severe peripheral vascular disease. Importantly, subgroup analysis is essential if the partial pressure of oxygen and the ankle-brachial index appear with a larger stratification.
- Findings from the microbial cultures of bone and deep soft tissue will be used to calculate the positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for a diagnosis of diabetic foot osteomyelitis. (1) Based on the sensitivity and specificity determined, these indicators will be used as an auxiliary of microbial cultures in the assessment of diabetic foot osteomyelitis. (2) A higher positive predictive value indicates a higher probability that the patient actually has the disease. (3) A higher negative predictive value indicates a higher probability that the patient does not have the disease. (4) When the positive likelihood ratio is > 10 or the negative likelihood ratio is < 0.1, there is a significant increase in the probability that the disease exists or does not exist, respectively.
The time schedule for outcome assessments is shown in [Table 2].
Data collection, management, analysis, and open access
- Data collection: All data will be collected on a case report form and summarized in one form. These data will include demographic information, disease diagnosis, concomitant diseases, allergic history (drug allergy), and adverse reactions. All data will be recorded electronically using a double-data entry strategy by EpiData software.
- Data management: Only the project manager will have the right to query the database, which will not be modified. All data relevant to this clinical trial will be saved by the Tianjin Metabolic Diseases Hospital of Tianjin Medical University.
- Data analysis: Statistical analysis will be completed by professional statisticians. The statistical results will be given to the project manager, who will be responsible for writing the research report. An independent data monitoring committee will be responsible for data monitoring and management throughout the entire trial to ensure scientific accuracy, authenticity, and integrity.
- Open data: All data will be released at http://www.figshare.com.
The statistical analysis will be completed by statisticians using the SPSS 19.0 statistical software (IBM Corp., Armonk, NY, USA) and will follow the intention-to-treat principle.
Normally distributed measurement data will be represented by mean, standard deviation, minimum value, and maximum value. Non-normally distributed data will be represented by the lower quartile, median, and upper quartile. Count data will be expressed as a percentage.
The test results on admission, including the microbiological and pathological tests of bone and surrounding deep soft tissue, blood biochemical tests, and detection of the blood supply, will be statistically compared using the Wilcoxon signed-rank test.
The sensitivity and specificity of the microbial cultures of the two types of tissues will be compared using the McNemar test, followed by the creation of receiver operating characteristic (ROC) curves. The better cut-off point will be selected as the diagnostic reference value. The closer the ROC curve is to the upper left corner, the higher the overall accuracy of the test. The area under the ROC curve is a measure of diagnostic accuracy. A value of P < 0.05 will be considered statistically significant.
- Predicted and unanticipated adverse reactions will be recorded during the trial.
- Adverse events will include dizziness, fever, nausea, and severe pain.
- All serious adverse events will be recorded in detail, including the date of occurrence, type of event, and treatments. All information will be reported to the project manager and the institution review board within 24 hours.
| Discussion|| |
This prospective, single-center, self-controlled, open clinical trial will attempt to determine the feasibility of using surrounding deep soft tissue instead of infected bone in microbiological and pathological examinations to diagnose diabetic foot osteomyelitis. The accuracy of this technique will be assessed by observing whether there is consistency between the microbiological and pathological findings for these two types of tissues in 200 patients with diabetic foot osteomyelitis. Findings from this trial will provide new insight into early diagnosis and proper use of antibiotics based on repeated diagnoses in patients with diabetic foot osteomyelitis. If consistency is high, this should prove beneficial for early diagnosis of diabetic foot osteomyelitis in patients who are uncooperative but scheduled for collection of infected bone tissue. In such patients, proper use of antibiotics will be guided by repeated diagnoses, thereby promoting foot ulcer healing. If consistency is low, this will mean that the surrounding deep soft tissues should not substitute for infected bone in microbiological and pathological tests. To affirm the accuracy of our results, further research using other methods will be performed in the future.
Recruitment of participants is ongoing at time of submission.
Conflicts of interest
JX conceived and designed the trial, wrote the paper, read and approved the final version of the paper for publication. SHF, XWL, WJY and ZXZ participated in case collection. MD, XML and JX were responsible for collecting and testing bone tissue and soft tissue samples. PHW was responsible for overall coordination and determination of the disputed judgment.
This paper was screened twice using CrossCheck to verify originality before publication.
This paper was double-blinded and stringently reviewed by international expert reviewers.
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[Table 1], [Table 2]