.../cyst positivity, especially in areas of necrosis ( fig. 25-6 ). Laboratory Diagnosis The use of the various laboratory diagnostic methods depends on the clinical setting, although two basic techniques are used: serology (measuring IgM, IgG, and IgA) and direct detection of the organism by means...

... myocarditis. Up to 40 percent of dilated cardiomyopathy cases are due to prior viral myocarditis ( 11 ). Pathologic Findings The patient selection for EMB requires consideration of the potential risks and risk-benefit ratio of the procedure. The indication for diagnostic biopsy for suspected myocarditis...

..., immunohistochemical assays, electron microscopy to identify scrapie-associated fibrils, and Western blot analysis (after proteinase K digestion) to detect the abnormal protein. The diagnostic tests are performed primarily on postmortem brain tissue, as the diagnostic features can be focal and not detected...

... the presence of hemozoin pigment is diagnostic. SEVERE MALARIA Figure 27-4 SEVERE MALARIA A–D: Granular red erythrocyte positivity on immunohistochemical staining in patients with severe malaria. (Courtesy of the CDC IDPB) Laboratory Diagnosis Rapid diagnostic tests (RDTs) have become the favored first...

... in diagnosing an infectious disorder has thus diminished considerably over the last decades. Despite this, the histopathologist is still often called on when other diagnostic modalities have failed to detect an etiology, or when findings detected by other less specific methodologies require confirmation...

... Diagnosis During acute disease or disease reactivation, where there is a high level of parasitemia, microscopic identification of parasitic forms in different body fluids and molecular testing are the diagnostic methods of choice. Examination for T. cruzi trypomastigotes in blood or cerebrospinal...

... diagnostic modalities include detection of S. pneumoniae polysaccharide antigens in urine and molecular testing (polymerase chain reaction [PCR]). STREPTOCOCCUS PNEUMONIAE Figure 12-5 STREPTOCOCCUS PNEUMONIAE Colonies on blood agar show alpha hemolysis (A), lysis after exposure...

... to quantify, since reporting is affected by geographic region, study design, sample size, incubation period, symptom severity, and the sensitivity of the diagnostic modality used ( 6 , 7 ). In one Brazilian study, 25 percent of tested individuals were seropositive for E. histolytica, with the highest...

... (replication enzymes: reverse transcriptase, integrase, and proteases): these provide the basis for diagnostic testing and drug treatment ( 1 ). HIV infection has been a major global health challenge for over 40 years. Although the syndrome was first described in the United States in 1981, transmission began...

... investigation, and microbiologic correlation are often necessary to differentiate reliably between these diagnostic possibilities. Laboratory Diagnosis Microbiologic culture is the gold standard for the diagnosis of brucellosis ( fig. 14-6 ), although special methods are required because of the intracellular...

... diagnostic value due to their long turnaround time, since most patients are dead by the time results are available. Similarly, the use of serology (detection of anti-RAV antibodies) in serum or CSF is also of limited value, as an antibody response is only present in late stages of the disease. The postmortem...

... ). Electron microscopy and culture are other diagnostic tools although these are, for the most part, limited to reference laboratories. EBOLA VIRUS IMMUNOHISTOCHEMISTRY Figure 10-4 EBOLA VIRUS IMMUNOHISTOCHEMISTRY A skin biopsy shows strong red positivity (A,B) and filamentous viral particles illustrated...

... in size from 20 to 100 μm and, depending on their maturity, contain one to hundreds of endospores, which measure 2 to 5 μm in diameter ( fig. 21-9 ). Mature spherules enclosing multiple endospores are diagnostic of coccidioidomycosis, but may require examination of multiple levels of numerous tissue bocks...

...), enzymatic, chemoluminescence, and line immunoassays. As treponemal tests have been automated, they are also included in screening guidelines. Treponemal tests can remain positive for years after an individual has had syphilis, however, which limits their diagnostic use in populations with high prevalence...

... in two settings: biopsies from suspected mucocutaneous disease (commonly sites where the organism is a commensal), and biopsy or resection tissue from patients with deep organ involvement (where finding any Candida or Candida-like yeasts is diagnostically significant). The inflammatory...

... ( 19 , 20 ). Although not in routine use, the sporotrichin skin test may serve as a diagnostic adjunct pending the outcome of fungal culture results ( 21 ). Prevention and Treatment Prevention of sapronotic infections relies on avoiding skin cuts and abrasions by using gloves, and wearing long sleeves...

... specimens, including vesicle fluid, blood, and cerebrospinal fluid (CSF). In addition, several molecular testing platforms are available. Direct immunofluorescence performed on cellular material scraped from a lesion is a rapid diagnostic tool ( fig. 6-7 ). The Tzanck smear uses Giemsa-stained cellular...

... patients with comorbidities. The clinical differential diagnosis of meningococcal meningitis includes bacterial meningitis due to other organisms, the most frequent being Streptococcus pneumoniae. In the case of meningococcemia, other diagnostic considerations include toxic shock, cellulitis...