Diagnostic sensitivity and specificity of the radionuclide (indium)-labeled leukocyte scan.

OBJECTIVE: Evaluate the sensitivity and specificity of Indium(111)-labeled leukocyte scans as used in a general, tertiary care hospital. METHODS: Retrospective review of electronic medical records from all patients who underwent Indium(111) scan at two large Veterans Affairs Medical Centers, 1999-2005, to determine congruence between Indium(111) scan readings and final clinical diagnoses, using all available data with at least 6 months of follow-up. RESULTS: Of 145 indium scans done for possible skeletal infection, infection was judged to be present in 52 cases. The sensitivity was 83%, and the specificity was 90%, with a diagnostic accuracy of 88%. Fifty-nine scans were done for indications other than skeletal infection. In 20 instances, when specific foci were suspected, the suspicion was correctly confirmed by indium scan in every case, without false positives or negatives (sensitivity and specificity, 100%). In 39 scans done to search for a possible source of nonspecific findings of infection (fever, leukocytosis, bacteremia), the sensitivity and specificity were 81% and 87%, respectively, with a diagnostic accuracy of 85%. CONCLUSION: Except as a means to confirm an already-suspected clinical focus, the indium scan appears to offer relatively little definitive information that can be used for diagnosis or treatment of infection.

Clostridium difficile lacks detectable superantigen activity.

Clostridium difficile colitis causes striking leukocytosis. We examined the possibility that toxins A or B, or other nontoxin products of C. difficile, act as superantigens, thereby stimulating leukocytosis. Our results failed to show major histocompatibility complex class II-dependent T lymphocyte proliferation, the hallmark of superantigen activity. Elevated white blood cell counts in C. difficile colitis are probably due to increased generation of cytokines such as interleukin-6 (IL-6) or IL-8.

Acute ischemic stroke and hypothyroidism.

BACKGROUND: In Kentucky, the incidence and mortality associated with stroke are among the highest in the United States. Treatment of modifiable risk factors can significantly prevent stroke. Identification of additional risk factors may further reduce stroke risk. Hypothyroidism is linked to altered lipid metabolism and is associated with hyperhomocysteinemia. In this study, we examined a possible association between acute ischemic stroke (AIS) and hypothyroidism. METHODS: Records were reviewed on all consecutive patients admitted to the University of Louisville Stroke Center with a diagnosis of AIS or transient ischemic attack (TIA). RESULT: Our data revealed that 12% of patients with AIS or TIA had hypothyroidism. A significant difference was found between the prevalence of hyperhomocysteinemia in patients with hypothyroidism (45.4%) compared with the prevalence of hyperhomocysteinemia in euthyroid patients (27.8%). CONCLUSION: Hypothyroidism is common in patients with AIS and TIA. Elevated homocysteine levels associated with hypothyroidism suggest that hypothyroidism may represent a modifiable stroke risk factor. Prospective studies are needed to verify this association.

Diagnostic value of microscopic examination of Gram-stained sputum and sputum cultures in patients with bacteremic pneumococcal pneumonia.

Clinicians continue to question the usefulness of microscopic examination of Gram-stained sputum specimens ("Gram staining") and sputum culture for diagnosis of pneumonia. We analyzed the sensitivity of these techniques in 105 patients with pneumococcal pneumonia proven by blood culture. Gram staining revealed gram-positive cocci in pairs and chains, and culture yielded pneumococci in only 31% and 44% of all cases, respectively. However, sputum specimens were never submitted for examination in 31 cases; in 16 others, the specimen was inadequate and a culture was not done. Excluding these cases, the sensitivities of Gram staining and culture were 57% and 79%, respectively. If patients receiving antibiotics for >24 h had been excluded, Gram staining would have suggested pneumococci in 63%, and culture results would have been positive in 86%. Sensitivity increased in inverse proportion to the duration of antibiotic therapy (P<.05). Microscopic examination of sputum samples before antibiotics were administered and performance of culture within 24 h of receipt of such treatment yielded the correct diagnosis in >80% of cases of pneumococcal pneumonia.

Clostridium difficile infection in patients with unexplained leukocytosis.

PURPOSE: To determine whether unrecognized Clostridium difficile infection is responsible for a substantial proportion of cases of unexplained leukocytosis in a tertiary care hospital setting. METHODS: We prospectively identified 60 patients who had unexplained leukocytosis (white blood cell count > or =15,000/mm3). Fecal specimens were tested for C. difficile toxin using an enzyme immunosorbent assay. We compared the clinical features of patients who had positive or negative assay results, as well as of 26 hospitalized control patients who did not have unexplained leukocytosis. RESULTS: Thirty-five (58%) of the patients with unexplained leukocytosis had C. difficile toxin in at least one fecal specimen as compared with 3 (12%) of the controls (P <0.001). Symptoms of colitis were often mild or absent at the time the white blood cell count was first elevated or, if present, had not been recognized by the attending physicians. Leukocytosis resolved promptly in most patients who were treated with metronidazole. In the 25 patients (42%) who had a negative test for C. difficile toxin, leukocytosis also tended to resolve during empiric therapy with metronidazole; some of these patients may have had C. difficile infection. CONCLUSION: The majority of patients in our hospital who had unexplained leukocytosis had C. difficile infection. Unexplained leukocytosis in hospitalized patients should prompt a search for symptoms and signs consistent with C. difficile infection and a study to detect C. difficile. Empiric therapy with metronidazole may be effective in the appropriate epidemiologic setting.

Conditions associated with leukocytosis in a tertiary care hospital, with particular attention to the role of infection caused by clostridium difficile.

Few modern studies have enumerated the conditions associated with leukocytosis. Our clinical experience has implicated Clostridium difficile infection in a substantial proportion of patients with leukocytosis. In a prospective, observational study of 400 inpatients with WBC counts of >/=15,000 cells/mm(3), we documented >/=1 infection in 207 patients (53%). Of these 207 patients, 97 (47%) had pneumonia, 60 (29%) had urinary tract infection, 34 (16%) had soft-tissue infection, and 34 (16%) had C. difficile infection. C. difficile infection was present in 25% of patients with WBC counts of >30,000 cells/mm(3) who did not have hematological malignancy. Other causes of leukocytosis in the 400 patients included physiological stress, in 152 patients (38%); medications or drugs, in 42 (11%); hematological disease, in 22 (6%); and necrosis or inflammation, in 22 (6%). C. difficile infection is a prominent cause of leukocytosis and this diagnosis should be considered for patients with WBC counts of >/=15,000 cells/mm(3), even in the absence of diarrheal symptoms.

Interaction between human polymorphonuclear leukocytes and Streptococcus milleri group bacteria.

Because Streptococcus milleri group (SMG) bacteria--Streptococcus constellatus, Streptococcus intermedius, and Streptococcus anginosus--exhibit a striking propensity to cause abscesses, the interaction of these organisms with human polymorphonuclear leukocytes (PMNL) was examined. After incubation in pooled normal human serum, SMG stimulated less chemotaxis than did Staphylococcus aureus, in contrast to viridans streptococci, which caused greater chemotaxis than did S. aureus. PMNL ingested greater numbers of SMG and viridans streptococci than S. aureus but killed these organisms more slowly and less completely. Relative resistance to killing by PMNL is expected in organisms that cause abscesses, and inhibition of chemotaxis may contribute to pathogenicity, because delayed arrival of PMNL gives a head start to proliferating bacteria. This study helps explain the capacity of SMG to cause abscesses. It is unclear, however, why viridans streptococci, bacteria that rarely produce abscesses, share some of these same properties.