Assay Sheet
Test ID
2000 Pneumocystis Real-time qPCR
CPT Code
87799
Clinical Utility
Pneumocystis jiroveci (formerly known as Pneumocystis carinii) pneumonia is a major cause of illness and death in individuals with impaired immune systems. Pneumocystis almost always affects the lungs, causing a form of pneumonia referred to as PCP. The organism that causes PCP has been renamed Pneumocystis jiroveci to reflect its new classification as a fungus. Quantitative DNA PCR is useful to detect the organism, track the course of infection, and monitor response to treatment.
Procedure
Extraction of Pneumocystis jiroveci DNA from bronchial lavage, or other respiratory specimens followed by amplification and detection using real-time, quantitative PCR. An internal control is added to ensure the extraction was performed correctly and the PCR reaction was not inhibited.
Specimens
BAL: 1-4 ml submitted in a sterile, leakproof tube; ship ambient.
Whole Blood: 3-5 ml submitted in an EDTA tube; ship ambient.
Other: Please inquire.
Specificity
The primers and probes used in this assay are specific for known Pneumocystis jiroveci strains based on similarity search algorithms. Additionally, no cross reactivity was detected with any viral or protozoa pathogens.
Pneumocystis jiroveci Assay Range
500 copies/ml to 1 x 1010 copies/ml
Turnaround Time
Within 24 hours of receiving specimen
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PCR tests are performed pursuant to a license agreement with Roche Molecular Systems, Inc.
This assay was developed and the performance characteristics were determined at ViraCor Laboratories. This test is performed in a CLIA certified laboratory. FDA approval is not required for the performance of this test.
AS16-0108
Pathogen Overview
ABOUT THE PNEUMOCYSTIS ORGANISM
Pneumocystis organisms were first discovered in the early 20th century. The organisms have been identified in virtually every mammalian species, but have genetic characteristics that make them host-specific. The pneumocystis that infects humans was named Pneumocystis carinii; the resulting disease became known as Pneumocystis carinii pneumonia, or PCP. At the time, P. carinii was classified as a protozoa based on morphologic features, lack of growth on fungal media and susceptibility to antiprotozoal drugs. However, accumulating molecular genetic data showed that P. carinii should be reclassified as a fungus, which resulted in renaming the organism to Pneumocystis jiroveci. P. jiroveci is now the accepted name for the causative agent of PCP in humans. The acronym ‘PCP’ has been maintained and redefined to refer to Pneumocystis pneumonia.
PNEUMOCYSTIS CLINICAL MANIFESTATIONS
Primary infection with P. jiroveci is very common and largely asymptomatic. Serological studies have shown nearly universal seropositivity by two years of age. Until recently, P. jiroveci was thought to remain latent within a person following primary infection and reactivate when the immune system became compromised. Mounting evidence has shown that person-to-person transmission, including asymptomatic carriers, is the most likely means of acquiring new infections. Acquisition from environmental sources may also occur. Symptomatic disease, which manifests as PCP, is only seen in immunocompromised patients: those infected with HIV, cancer patients receiving chemotherapy, bone marrow and solid organ transplant recipients, as well as patients treated with corticosteroids and other immune suppressive agents. PCP is often the AIDS-defining illness in HIV patients, though the incidence has decreased due to the advent of HAART and prophylaxis. However, the incidence of PCP in non-HIV immunocompromised patients is increasing.
PCP most commonly presents as low-grade fever, dyspnea and cough. Physical examination often reveals tachypnea, tachycardia, and normal findings on lung auscultation. Hypoxemia is often found. The typical PCP x-ray shows diffuse, bilateral, fluffy infiltrates predominantly centrally located. Less common clinical presentations include extrapulmonary pneumocystis, such as hepatic pneumocystis, nodular granulomatous PCP and pleural effusions. Presentation of PCP in HIV patients is subtle, lasting from weeks to months, with a mortality rate of 10 to 20%. In non-HIV immunocompromised patients, PCP presents abruptly as respiratory failure, with a mortality rate of 30 to 60%.
PNEUMOCYSTIS LABORATORY DIAGNOSIS
P. jiroveci cannot be cultured in vitro. Therefore, routine diagnostics have relied upon microscopic examination of bronchoalveolar lavage (BAL) fluid or induced sputum utilizing either Giesma or direct immunfluorescence staining (DFA). However, these methods are technically difficult and dependent upon the quality of the sample. P. jiroveci infected cells disintegrate after a few hours; samples older than 3 hours must be rejected due to the increased risk of false negative results. Recently developed quantitative real-time PCR assays have the highest level of sensitivity and specificity and are gradually replacing microscopic techniques. In addition, quantitative real-time PCR offers the ability to monitor the patient’s response to treatment over time. Lung biopsy tissue or BAL fluid are the specimens of choice for quantitative real-time PCR diagnosis.
PNEUMOCYSTIS TREATMENT
Prophylaxis against PCP in HIV-infected patients is recommended when the CD4+ count is less than 200 cells/mm3 or if there is a history of oropharyngeal candidiasis. Prophylaxis is also recommended for transplant patients. Trimethoprim-sulfamethoxazole (TMP-SMX) is considered first-line therapy in the prophylaxis of PCP. Intolerance and resistance to TMP-SMX can limit its use. Aerosolized pentamidine and altovaquone suspension have been used as alternatives. PCP prognosis depends on the amount of damage to the lungs prior to treatment.
Selected References
Bandt D, Monecke S. Development and evaluation of a real-time PCR assay for detection of Pneumocystis jiroveci. Transpl Infect Dis. 2007;(9):196-202.
Green H, Paul M, Vidal L, Leibovici L. Prophylaxis for pneumocystis pneumonia (PCP) in non-HIV immunocompromised patients. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005590. DOI: 10.1002/14651858.CD005590.pub2.
Höcker B, Wendt C, Nahimana A, Tönshoff B, Hauser PM. Molecular evidence of Pneumocystis transmission in pediatric transplant unit. Emerg Infect Dis. 2005;11(2):330-332.
Stringer JR, Beard CB, Miller RF, Wakefield AE. Perspective: a new name (Pneumocystis jiroveci) for pneumocystis from humans. Emerg Infect Dis. 2002;(8):891-896.
Thomas CF, Limper AH. Pneumocystis pneumonia. N Engl J Med. 2004;(350):2487 –2498.
PAO-15-0807 PCR tests are performed pursuant to a license agreement with Roche Molecular Systems, Inc.
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Abstracts & Publications
Bandt D, Monecke S. Development and evaluation of a real-time PCR assay for detection of Pneumocystis jiroveci. Transpl Infect Dis.2007;(9):196-202.
Green H, Paul M, Vidal L, Leibovici L. Prophylaxis for pneumocystis pneumonia (PCP) in non-HIV immunocompromised patients. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005590. DOI: 10.1002/14651858.CD005590.pub2.
Höcker B, Wendt C, Nahimana A, Tönshoff B, Hauser PM. Molecular evidence of Pneumocystis transmission in pediatric transplant unit. Emerg Infect Dis. 2005;11(2):330-332.
Stringer JR, Beard CB, Miller RF, Wakefield AE. Perspective: a new name (Pneumocystis jiroveci) for pneumocystis from humans. Emerg Infect Dis. 2002;(8):891-896.
Thomas CF, Limper AH. Pneumocystis pneumonia. N Engl J Med. 2004;(350):2487 –2498
Pneumocystis jiroveci (formerly known as Pneumocystis carinii) pneumonia is a major cause of illness and death in persons with impaired immune systems. Pneumocystis almost always affects the lungs, causing a form of pneumonia referred to as PCP. The organism that causes PCP has been renamed Pneumocystis jiroveci to reflect its new classification as a fungus. ViraCor’s quantitative Pneumocystis jiroveci DNA PCR assay is used to detect the organism, track the course of infection, and monitor response to treatment.