Applications of fluorodeoxyglucose positron emission tomography in the diagnosis of infection

Orthopedic surgery-related benign uptake on FDG-PET: case examples and pitfalls

Orthopedic surgical procedures often create some special postoperative complications, which may demonstrate abnormally increased or focal uptake for an extended period of time on FDG PET-CT images. The distinction of normal from pathologic, benign from malignant uptake is very important to minimize the number of false positive results. To date, very little data have been published regarding surgical-related benign musculoskeletal uptake on PET-CT imaging. In this paper, we present to the readers some case examples of FDG PET-CT imaging for postoperative fracture, infection or osteomyelitis, metallic implants, aggressive bone edge, heterotopic ossification, granuloma and neuroma. We also discuss potential pitfalls to recognize these orthopedic surgery-related complications and identify benign nature of increased FDG uptake. In all cases, the patient's medical and surgical history would be of paramount importance to the radiologists/nuclear medicine physicians who interprets the scan. It is also crucial to carefully correlate FDG uptake with the anatomy on the co-registered CT images in all transaxial, coronal and sagittal views in order to identify the location and pattern of uptake.

FDG-PET for diagnosing prosthetic joint infection: systematic review and metaanalysis

PURPOSE

The aim of this study was to systematically review and metaanalyze published data on the diagnostic performance of (18)F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET) in detecting prosthetic hip or knee joint infection.

METHODS

A systematic search for relevant studies was performed of the PubMed/MEDLINE and Embase databases. Two reviewers independently assessed the methodological quality of each study. A metaanalysis of the reported sensitivity and specificity of each study was performed. Subgroup analyses were performed if results of individual studies were heterogeneous.

RESULTS

The inclusion criteria were met by 11 studies; there was a total sample size of 635 prostheses. Overall, the studies had good methodological quality. Pooled sensitivity and specificity of FDG-PET for the detection of prosthetic hip or knee joint infection were 82.1% (95%CI = 68.0-90.8%) and 86.6% (95%CI = 79.7-91.4%), respectively. Heterogeneity among the results of individual studies was present (I (2) = 68.8%). Diagnostic performance was influenced by type of joint prostheses (hip prostheses vs. knee prostheses) and type of reconstruction method used (filtered back vs. iterative) (p = 0.0164 and p = 0.0235, respectively).

CONCLUSION

In this metaanalysis, overall diagnostic performance of FDG-PET was moderate to high. Caution is warranted, however, because results of individual studies were heterogeneous and could not be fully explored. Future studies should further explore potential causes of heterogeneity and validate the use of FDG-PET for diagnosing prosthetic joint infection.

Interobserver reproducibility in the interpretation of 99mTc-labelled white blood cell scintigraphic images

OBJECTIVE

This study was performed to investigate the interobserver reproducibility of the interpretation of Tc-labelled white blood cell scans combined or not with other nuclear medicine procedures.

METHODS

Twenty nuclear medicine physicians working in Belgium received clinical data and scintigraphic images from 10 patients suspected of suffering from various infectious diseases. They had to choose, for each patient, one answer among 'high probability', 'intermediate probability' and 'low probability' of infection. In a first step the level of agreement, defined as the highest percentage obtained among the three proposed answers, was calculated for each case; complete agreement was arbitrarily defined when 80% or more of the observers gave the same answer. In a second step, a numerical score was given for each answer and for each observer. The scores were defined as 0 for the 'low probability' answer, 1 for the 'intermediate probability' and 2 for the 'high probability' answer. The scores of each observer were summed up allowing obtaining of a cumulated score for each observer; observers were thereafter classified as a function of their own cumulated score.

RESULTS

An agreement of 80% or more was observed only in three patients. The cumulated scores of the observers were between 4 and 16, demonstrating that some observers were more sensitive than others.

CONCLUSION

Interobserver reproducibility in the interpretation of the white blood cell scan was poor; several factors could explain these results, the most frequent being both the poor specificity of the labelled white blood cell scan and different concepts in interpreting combined nuclear medicine procedures in several situations. As observers received the anonymized overall results, this study may have a favourable impact on continuing education in medical imaging.

Is F 18 Fluorodeoxyglucose Positron Emission Tomography Too Sensitive for the Diagnosis of Vascular Endograft Infection?

We report a case of a false positive fluorodeoxyglucose positron emission tomography (FDG-PET) scan in a patient who presented with abdominal pain, and gastrointestinal bleeding accompanied by elevation of inflammatory markers, seven weeks after a proximal type I endoleak repair with a cuff extension. Aortoenteric fistula and endograft infection was ruled out by laparotomy. FDG-PET image may have a role in diagnosis of infection, but false positive results are possible and caution is necessary if other data are non-confirmatory.

Diagnosis and localization of renal cyst infection by 18F-fluorodeoxyglucose PET/CT in polycystic kidney disease

Renal cyst infection in polycystic kidney disease is a serious complication. Early diagnosis and localization of infected cyst are crucial and usually require conventional imaging modalities, including ultrasound and computed tomography (CT). However, their contribution is limited because of nonspecific results. We report on a patient with suspected renal cyst infection for which 18F-fluorodeoxyglucose positron emission tomography (FDG-PET)/CT scan allowed the exact localization of the infected cyst and guided a drainage procedure. FDG-PET/CT imaging could be a valuable tool for early identification of infected renal cyst infection, and may contribute to better patient management.

Role of modern imaging techniques for diagnosis of infection in the era of 18F-fluorodeoxyglucose positron emission tomography

During the past several years, it has become quite evident that positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) imaging can play a major role in the management of patients with suspected infection. Particularly, several groups have demonstrated that this powerful imaging methodology is very effective in the evaluation of osteomyelitis, infected prostheses, fever of unknown origin, and AIDS. In view of its extraordinary sensitivity in detecting disease activity and the ability to quantitate the degree of FDG uptake, PET might prove to be an appropriate modality for monitoring disease activity and evaluating response to therapy. FDG-PET has many advantages over existing imaging techniques for the diagnosis of infectious diseases. These include feasibility of securing diagnostic results within 1.5 to 2 h, excellent spatial resolution, and accurate anatomical localization of sites of abnormality. The availability of PET/computed tomography as a practical tool has further enhanced the role of metabolic imaging in many settings. In the future, this modality is very likely to be employed on a routine basis for detecting, characterizing, and monitoring patients with suspected and proven infection.

Critical role of 18F-labeled fluorodeoxyglucose PET in the management of patients with arthroplasty

The most frequent complications after arthroplasty are aseptic loosening and infection. It is often difficult to differentiate aseptic loosening from infection. The management of these two distinct clinical identities is quite different, however. Treatment of aseptic loosening usually requires one-step revision surgery, whereas treatment of infection requires antimicrobial therapy for an extended period before inserting a new prosthesis. Infection associated with arthroplasty is a serious complication and should be treated adequately before proceeding with a surgical intervention. PET with 18F-labeled fluorodeoxyglucose (FDG) has been proposed as an accurate technique for evaluating painful arthroplasty. This review addresses the applications of FDG-PET in such clinical settings. In addition, the potential of PET in the assessing the viability of bone grafts in revision arthroplasty is discussed.

The Use of Positron Emission Tomography With (18)F-Fluorodeoxyglucose for the Diagnosis of Vascular Graft Infection

Vascular graft infection is associated with a high morbidity and mortality rate. Diagnosis is difficult, as there is no single diagnostic criterion that has a 100% accuracy. A combination of physical examination, laboratory tests, and several imaging techniques is mandatory. Beside a wide range of indications in the oncological field, positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) has a well-known role in the diagnosis of bone and soft-tissue infections. Some authors have recently reported on the potential use of FDG-PET in the diagnosis of vascular graft infections. The aim of this study is to review personal experience. Five consecutive patients with a suspected prosthetic infection (1 aortobifemoral bypass, 3 femoropopliteal bypasses, and 1 femorofemoral bypass) underwent FDG-PET. All prostheses showed a moderate or intense FDG tracer uptake. All 3 patients with an intense FDG uptake proved to have a prosthetic infection (based on microbiologic examination). These preliminary results suggest that FDG-PET might be an interesting tool to confirm vascular graft infection.

New imaging tools for the diagnosis of infection

Infection imaging became widespread in 1971 with the release of 67Ga citrate. Multiphase skeletal scintigraphy and radiolabeled white blood cells (WBCs) have since become the most widespread clinically used agents for the imaging of infection. A wide variety of other radiolabeled probes are under investigation, based on antibodies, cytokines, assorted proteins and other molecules, alone or in various combinations. However, these latter agents, with a few exceptions, are not routinely used clinically. Radiolabeled ciprofloxacin represents the first attempt to develop an infection-specific imaging agent (most infection-imaging probes localized nonspecifically to inflammation as well), but it has not proven superior to radiolabeled WBCs or 18F-fluoro-deoxy-glucose (FDG) PET. Because of the ability to combine exquisite anatomic detail with focal uptake of 18F-FDG, PET–computed tomography has achieved great success in the detection and localization of infection, including in clinically adverse conditions. Despite these advances, at this time an infection-specific imaging agent does not exist.

[Positron emission tomography in internal medicine]

FDG-PET is now an established diagnostic tool in oncology. Fluorodeoxyglucose is not a specific tracer for malignant lesions but rather for elevated glucose metabolism, present not only in cancer but also in inflammatory and infectious lesions. FDG-PET has thus been suggested for diagnosis of fevers of unknown origin, deep bone or visceral infectious foci, inflammatory vasculitis or sarcoidosis and unknown primary tumors, all frequent situation in internal medicine. The main characteristics of FDG-PET are its ability to rule out focal inflammation or infection with a high degree of certainty when the examination is negative because of its good negative predictive value and its usefulness as an early marker of therapeutic response, compared with anatomy-based or conventional scintigraphic imaging. Large-scale prospective studies are necessary, however, before FDG-PET is integrated into routine clinical use. It should be compared with different techniques already validated (biology, radiology, conventional scintigraphic imaging) and its cost-effectiveness should be evaluated.

Radionuclide imaging of spinal infections

BACKGROUND

The diagnosis of spinal infection, with or without implants, has been a challenge for physicians for many years. Spinal infections are now being recognised more frequently, owing to aging of the population and the increasing use of spinal-fusion surgery.

DISCUSSION

The diagnosis in many cases is delayed, and this may result in permanent neurological damage or even death. Laboratory evidence of infection is variable. Conventional radiography and radionuclide bone imaging lack both sensitivity and specificity. Neither in vitro labelled leucocyte scintigraphy nor 99mTc-anti-granulocyte antibody scintigraphy is especially useful, because of the frequency with which spinal infection presents as a non-specific photopenic area on these tests. Sequential bone/gallium imaging and 67Ga-SPECT are currently the radionuclide procedures of choice for spinal osteomyelitis, but these tests lack specificity, suffer from poor spatial resolution and require several days to complete. [18F]Fluoro-2-deoxy-D-glucose (FDG) PET is a promising technique for diagnosing spinal infection, and has several potential advantages over conventional radionuclide tests.

RESULTS

The study is sensitive and is completed in a single session, and image quality is superior to that obtained with single-photon emitting tracers. The specificity of FDG-PET may also be superior to that of conventional tracers because degenerative bone disease and fractures usually do not produce intense FDG uptake; moreover, spinal implants do not affect FDG imaging. However, FDG-PET images have to be read with caution in patients with instrumented spinal-fusion surgery since non-specific accumulation of FDG around the fusion material is not uncommon.

CONCLUSION

In the future, PET-CT will likely provide more precise localisation of abnormalities. FDG-PET may prove to be useful for monitoring response to treatment in patients with spinal osteomyelitis. Other tracers for diagnosing spinal osteomyelitis are also under investigation, including radiolabelled antibiotics, such as 99mTc-ciprofloxacin, and radiolabelled streptavidin-biotin complex. Antimicrobial peptides display preferential binding to microorganisms over human cells and perhaps new radiopharmaceuticals will be recruited from the array of human antimicrobial peptides/proteins. In experiments with Tc-ubiquicidin-derived peptides, radioactivity at the site of infection correlated well with the number of viable bacteria present. Finally, radiolabelled antifungal tracers could potentially distinguish fungal from bacterial infections.

Fluordeoxyglucose positron emission tomography contributes to management of pediatric liver transplantation candidates with fever of unknown origin

Fever of unknown origin (FUO) frequently complicates the management of pediatric patients with terminal chronic liver failure during the pretransplantation period and may lead to increased morbidity and mortality. Nonhepatic origins of systemic infections may render the patient unsuitable for transplantation whereas infections within the liver may require organ resection for a cure. Therefore, accurate localization of the infection focus is critical for optimal management of children on the waiting list for liver transplantation. Here we report our experience using [18 F]fluordeoxyglucose (FDG)-positron emission tomography (PET) to detect the origin of infection in 11 children with biliary cirrhosis presenting with FUO during the waiting period for liver transplantation. In 5 children, positive intrahepatic FDG-PET signals correlated with bacterial cultures of the excised liver and/or anatomic or histologic signs of infection. Based on the FDG-PET findings, these patients underwent transplantation after continuous antibiotic treatment with ongoing, recurrent episodes of fever. In 6 children, no abnormal hepatic FDG-PET signals were found and no infections could be detected in the liver. Transplantation in these patients was performed only after becoming afebrile. Standard imaging techniques did not reveal abnormalities compatible with infection in any of the children. In conclusion, in children with biliary cirrhosis and FUO on the waiting list for liver transplantation, information obtained by FDG-PET imaging may be useful for decisions on therapy and suitability for liver transplantation.

Nuclear medicine imaging of bone infections

The inflammation and infection of bone include a wide range of processes that can result in a reduction of function or in the complete inability of patients. Apart from the inflammation, infection is sustained by pyogenic microorganisms and results mostly in massive destruction of bones and joints. The treatment of osteomyelitis requires long and expensive medical therapies and, sometimes, surgical resection for debridement of necrotic bone or to consolidate or substitute the compromised bones and joints. Radiographs and bone cultures are the mainstays for the diagnosis but often are useless in the diagnosis of activity or relapse of infection in the lengthy management of these patients. Imaging with radiopharmaceuticals, computed tomography and magnetic resonance are also used to study secondary and chronic infections and their diffusion to soft or deep tissues. The diagnosis is quite easy in acute osteomyelitis of long bones when the structure of bone is still intact. But most cases of osteomyelitis are subacute or chronic at the onset or become chronic during their evolution because of the frequent resistance to antibiotics. In chronic osteomyelitis the structure of bones is altered by fractures, surgical interventions and as a result of bone reabsorption produced by the infection. Metallic implants and prostheses produce artefacts both in computed tomography and magnetic resonance images, and radionuclide studies should be essential in these cases. Vertebral osteomyelitis is a specific entity that can be correctly diagnosed by computed tomography or magnetic resonance imaging at the onset of symptoms but only with radionuclide imaging is it possible to assess the activity of the disease after surgical stabilization or medical therapy. The lack of comparative studies showing the accuracy of each radiopharmaceutical for the study of bone infection does not allow the best nuclear medicine techniques to be chosen in an evidence-based manner. To this end we performed a meta-analysis of peer reviewed articles published between 1984 and 2004 describing the use of nuclear medicine imaging for the study of the most frequent causes of bone infections, including prosthetic joint, peripheric post-traumatic bone infections, vertebral and sternal infections. Guidelines for the choice of the optimal radiopharmaceuticals to be used in each clinical condition and for different aims is provided.

The value of FDG-PET and bone scintigraphy with SPECT in the primary diagnosis and follow-up of patients with chronic osteomyelitis of the mandible

OBJECTIVE

To appraise the value of FDG-PET and bone scintigraphy using SPECT in the primary diagnosis and follow-up of patients with chronic osteomyelitis of the mandible (COM).

METHODS

In a prospective study the pattern of tracer uptake was investigated using 2 diagnostic methods in 42 patients. Results were compared with histology and radiographs as well as clinical and laboratory parameters.

RESULTS

The use of FDG-PET in the primary diagnosis of COM resulted in a sensitivity of 64% and a specificity of 77.7%. The sensitivity of SPECT was 84% and the specificity 33.3%. During the follow-up period of these patients the sensitivity of SPECT increased to 93.7%, while the specificity decreased (6.6%). The sensitivity and specificity of FDG-PET for this follow-up group were 62.5 and 80%, respectively.

CONCLUSION

Because of its high sensitivity, SPECT is vastly superior to other diagnostic methods in initiating treatment. In the follow-up period it might be replaced by FDG-PET, which reflects the disease course better and indicates the time of clinical remission.

Deep-seated resistance in relapsed paratyphoid fever

We describe a case of relapsed paratyphoid fever in which the isolate had reduced susceptibility to ciprofloxacin due to a rare mutation within the gyrA gene. 18fluorodeoxyglucose positron emission tomography scanning identified deep-seated infection including unsuspected aortitis and highlights the utility of novel imaging techniques to improve our understanding and treatment of this disease.

Early detection of bone infection and differentiation from post-surgical inflammation using 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography (FDG-PET) in an animal model

Diagnosing bone infection in the context of post-surgical inflammation is problematic since many of the early signs of infection are similar to normal post-surgical changes. We used a rabbit osteomyelitis model to evaluate the use of 2-deoxy-2-[(18)F]-fluoro-d-glucose positron emission tomography (FDG-PET) as a means of detecting post-operative infection in the context of post-surgical inflammation. Comparisons were made between infected and non-infected rabbits in which infection with Staphylococcus aureus was initiated at the time of surgery. Weekly PET scans were obtained 30 and 60 min after the introduction of FDG and analyzed based on standardized uptake values (SUV) at the surgical site and visual assessment of the presence or absence of infection. Concurrent X-rays were taken immediately prior to scanning. At 4weeks post-operatively, animals were sacrificed for histologic and bacteriologic confirmation of infection. Uptake of FDG was evident in the bone of all rabbits on day 1 post-surgery, however, SUV comparisons from the surgical site could not be used to distinguish between the infected and uninfected groups until day 15. Visual analysis of FDG-PET scans revealed a significant difference (p<0.01) between the infected and uninfected groups as early as day 8. This was due in part to the ability to visualize regional lymph nodes by FDG-PET.

Gammagrafía con 99mTc-ceftizoxima en ratas normales y en ratas con absceso inducido

This study aimed to investigate the biodistribution of the 99mTc-ceftizoxime in normal rats and in rats bearing septic and sterile induced abscess.

MATERIAL AND METHODS

Three groups of rats were studied. a) Six normal rats b) 15 rats with E. coli induced abscess and c) 15 rats with sterile zymosan induced abscess. Septic abscess was induced with 2 x 10(8) colony forming units of E. coli and sterile one with 0.1 mL of 5% sterile Zymosan. 24 h after the abscess induction, 12 MBq of 99mTc-CFT were injected iv. and whole body images were collected at 30 min, 1, 2, 4 and 6 h p.i. Areas of interest were drawn and lesion/background index was calculated. The 6 normal rats were scanned at the same times, killed at 6 h p.i and kidney, liver, spleen, lung, heart and muscle activity were measured. Each organ was weighed, cut and its activity measured. Parallelly, the biological activity of the labeled antibiotic and its binding to the E. coli and S. aureus bacteria were analyzed.

RESULTS

High biliary excretion was seen in all rats. Organ measurement showed the maximal uptake in kidney and very low uptake in muscles. Mean +/- s.d abscess/background ratio at 30 min, 1, 2, 4 and 6 h were 2.60 +/- 0.36, 2.67 +/- 0.66, 2.6 0 +/- 0.58, 2.78 +/- 0.84, 3.24 +/- 1.00 for septic abscess and 2.37 +/- 0.39, 2.10 +/- 0.38, 1.97 +/- 0.34, 1.82 +/- 0.25, 1.65 +/- 0.23 for aseptic abscess. The 99mTc-CFT uptake was significantly higher in the septic abscess than in sterile one (p < 0.05). The 99mTc-CFT uptake in the septic abscess remains stable or increases until along the 6 h. The 99mTc-CFT uptake in the aseptic abscess decreases along the time.

CONCLUSIONS

The scintigraphy with 99mTc-CFT seems able to differentiate sterile inflammation from infection. High biliary excretion limits its application in abdomen. Main application could be diagnosis of osteoarticular infection.

Influence of ceftriaxone treatment on FDG uptake--an in vivo [18F]-fluorodeoxyglucose imaging study in soft tissue infections in rats

Our aim was to determine the influence of antibiotic treatment using ceftriaxone on [18F]-fluorodeoxyglucose (FDG) uptake in experimental soft tissue infections. PET scans were performed in two groups (treated n=4; non-treated n=4) at days 3, 5, and 6 after inoculation of the infection. Additional autoradiography was performed in four animals at day 7 and in three animals at day 11. The difference of FDG uptake on day 5 (after three days of antibiotic treatment) between both groups proved to be significant (df=6; T=2.52; p=0.045). FDG uptake determined at the other days did not reveal significant difference between the two groups. It seems to be possible that the effect of antibiotic treatment on FDG uptake is less evident than reported for therapy monitoring of cancer treatment. The change of FDG uptake over time in treated and untreated infections is complex and further in vivo experiments have to be initiated to investigate the potential value of clinical FDG PET in therapy monitoring of infection.

Evolving role of positron emission tomography in the management of patients with inflammatory and other benign disorders

Fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has evolved from a research imaging modality assessing brain function in physiologic and pathologic states to a pure clinical necessity. It has been successfully used for diagnosing, staging, and monitoring a variety of malignancies. FDG-PET imaging also is evolving into a powerful imaging modality that can be effectively used for the diagnosis and monitoring of a certain nononcological diseases. PET has been shown to be very useful in the diagnosis of osteomyelitis, painful prostheses, sarcoidosis, fever of unknown etiology, and acquired immunodeficiency syndrome. Based on recent observations, several other disorders, such as environment-induced lung diseases, atherosclerosis, vasculitis, back pain, transplantation, and blood clot, can be successfully assessed with this technique. With the development and the introduction of several new PET radiotracers, it is expected that PET will secure a major role in the management of patients with inflammatory and other benign disorders.

Diagnosis of vascular prosthesis infection with FDG-PET/CT

Fluorodeoxyglucose positron emission tomography (FDG-PET) is on the verge of becoming an established imaging tool in the fields of clinical oncology, cardiology, and neurology. Because of the high glucose uptake of inflammatory cells, FDG scanning is an appropriate tool for use in tracing suspected inflammation or to evaluate infection. PET, although highly sensitive, often lacks the ability to define the precise anatomic location of abnormal FDG accumulation. The new PET/computed tomography (CT) technology provides precise registration of metabolic and structural imaging data in a single session. We report positive FDG-PET/CT findings in an infected vascular prosthesis 6 months after grafting. Our experience and a few available case reports support the hypothesis that FDG-PET/CT may have a promising role in future noninvasive diagnosis of infected vascular grafts.

Normal variants in [18F]-fluorodeoxyglucose PET imaging

The number of fluorodeoxyglucose PET applications is increasing. In the process of reading fluorodeoxyglucose-PET scans, nuclear medicine physicians encounter a wide variety of normal findings, which must be recognized to determine the best management for patients. It is important to recognize and understand normal variants to avoid misinterpretation of more serious pathology. This article reviews different patterns of physiologic fluorodeoxyglucose uptake including changes with age.

Clinical value of FDG PET in patients with fever of unknown origin and patients suspected of focal infection or inflammation

Fever of unknown origin (FUO) and suspected focal infection or inflammation are challenging medical problems. The aim of this study was to assess the value of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) in patients with FUO and patients with suspected focal infection or inflammation. All FDG PET scans ordered because of FUO or suspected focal infection or inflammation in the last 4 years were reviewed. These results were compared with the final diagnosis. Thirty-five FDG PET scans were performed in 35 patients with FUO. A final diagnosis was established in 19 patients (54%). Of the total number of scans, 37% were clinically helpful. The positive predictive value of FDG PET in these patients was 87% and the negative predictive value was 95%. Fifty-five FDG PET scans were performed in 48 patients with suspected focal infection or inflammation. A final diagnosis was established in 38 patients (82%). Of the total number of scans, 65% were clinically helpful. The positive predictive value of FDG PET in these 55 episodes of suspected infection or inflammation was 95% and the negative predictive value was 100%. It is concluded that FDG PET appears to be a valuable imaging technique in the evaluation of FUO and suspected focal infection or inflammation. Furthermore, FDG PET could become a useful tool for evaluating the effect of treatment of infectious and inflammatory processes that cannot reliably be visualised by conventional techniques. However, to assess the additional diagnostic value of this technique, prospective studies of FDG PET as part of a structured diagnostic protocol are warranted.