title: Comparison of a real-time PCR method with serology and blood smear analysis for diagnosis of human anaplasmosis: importance of infection time course for optimal test utilization.
abstract: Anaplasmosis and ehrlichiosis are emerging tick-borne diseases with clinically similar presentations caused by closely related pathogens. Currently, laboratories rely predominantly on blood smear analysis (for the detection of intracellular morulae) and on serologic tests, both of which have recognized limitations, for diagnostic purposes. We compared the performance of a published real-time PCR assay that incorporates melt curve analysis to differentiate Anaplasma and Ehrlichia species with blood smear and serologic methods in an upper Midwest population. Overall, 38.5% of the specimens selected for evaluation had one or more tests that were positive for anaplasmosis. The PCR positivity for all specimens was maximal (21.2%; 29/137) during the early acute phase of illness (0 to 4 days since illness onset) and significantly less frequent (11.5%; 20/174) during later phases (>4 days since illness onset). All positive specimens were Anaplasma phagocytophilum; no Ehrlichia species were identified. The real-time PCR detected 100% of infections that were detected by blood smear analysis (14/14) and broadened the detection window from a maximum of 14 days for smear positivity to 30 days for PCR. Additional infections were detected by real-time PCR in 12.9% (11/85) of smear-negative patients. There was poor agreement between the real-time PCR assay and serologic test results: 19.8% (19/96) and 13.7% (29/212) of seropositive and -negative patients, respectively, were PCR positive. Seropositivity increased with increasing days of illness, demonstrating that serologic detection methods are best utilized during presumed convalescence. Our results indicate that the optimal performance and utilization of laboratory tests for the diagnosis of anaplasmosis require knowledge regarding time of symptom onset or days of illness.
authors: Marshfield Clinic Research Foundation, Marshfield, Wisconsin, USA. schotthoefer.anna@mcrf.mfldclin.edu
authors: A M
authors: AM
authors: Schotthoefer
authors: J K
authors: JK
authors: Meece
authors: L C
authors: LC
authors: Ivacic
authors: P D
authors: PD
authors: Bertz
authors: K
authors: K
authors: Zhang
authors: T
authors: T
authors: Weiler
authors: T S
authors: TS
authors: Uphoff
authors: T R
authors: TR
authors: Fritsche
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D041081:Anaplasma phagocytophilum / Q000302:isolation & purification*; D000712:Anaplasmosis / Q000175:diagnosis*; D001431:Bacteriological Techniques / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008853:Microscopy / Q000379:methods*; D008875:Middle Aged; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012698:Serologic Tests; D013997:Time Factors; D055815:Young Adult
references: J Clin Microbiol. 1999 Sep;37(9):2968-73
references: 10449483
references: Clin Infect Dis. 2002 Jan 1;34(1):22-7
references: 11731941
references: N Engl J Med. 2011 Aug 4;365(5):422-9
references: 21812671
references: Clin Infect Dis. 2007 Jul 15;45(2):199-204
references: 17578779
references: Curr Opin Pediatr. 2009 Feb;21(1):102-11
references: 19242246
references: Mol Diagn. 1996 Jun;1(1):41-49
references: 10330196
references: J Med Entomol. 2004 Nov;41(6):1104-10
references: 15605650
references: JAMA. 1996 Jan 17;275(3):199-205
references: 8604172
references: Diagn Microbiol Infect Dis. 2005 Dec;53(4):301-6
references: 16263231
references: J Clin Microbiol. 1994 Mar;32(3):589-95
references: 8195363
references: MMWR Recomm Rep. 2006 Mar 31;55(RR-4):1-27
references: 16572105
references: Anal Bioanal Chem. 2009 Jun;394(3):731-42
references: 19377839
references: Clin Infect Dis. 1998 Dec;27(6):1491-6
references: 9868666
references: Clin Infect Dis. 2000 Aug;31(2):554-60
references: 10987720
references: Clin Microbiol Rev. 2003 Jan;16(1):37-64
references: 12525424
references: Parasit Vectors. 2012 Feb 08;5:29
references: 22316160
references: WMJ. 2011 Apr;110(2):82-4
references: 21560563
references: Clin Infect Dis. 2001 Mar 15;32(6):862-70
references: 11247709
references: J Clin Microbiol. 1999 Mar;37(3):558-64
references: 9986812
references: MMWR Morb Mortal Wkly Rep. 1995 Aug 11;44(31):590-1
references: 7623762
references: Vector Borne Zoonotic Dis. 2002 Winter;2(4):233-9
references: 12804164
references: Expert Rev Mol Diagn. 2004 Jul;4(4):559-69
references: 15225103
references: J Clin Microbiol. 2000 Feb;38(2):635-8
references: 10655359
references: Open Microbiol J. 2011;5:18-20
references: 21643499
references: Clin Infect Dis. 2007 Jul 15;45 Suppl 1:S45-51
references: 17582569
references: Expert Rev Anti Infect Ther. 2009 Aug;7(6):709-22
references: 19681699
references: Am J Trop Med Hyg. 2011 Jul;85(1):124-31
references: 21734137
references: Ann N Y Acad Sci. 2006 Oct;1078:236-47
references: 17114714
references: J Clin Microbiol. 1999 Jan;37(1):31-4
references: 9854059
references: N Engl J Med. 1999 Jul 15;341(3):148-55
references: 10403852
references: Antimicrob Agents Chemother. 2001 Jul;45(7):2098-105
references: 11408229