CBER Presentation
CDC Experience with Laboratory Tests Used to Investigate Incidents of Transfusion-Transmitted Malaria
FDA Workshop on Testing for Malarial Infections in Blood Donors
July 12, 2006
Marianna Wilson
Division of Parasitic Diseases
Centers for Disease Control and Prevention
Atlanta, GA
DIAGNOSTIC TOOLS AVAILABLE AT CDC
- Blood film examination
- Antibody detection - IFA
- DNA detection - PCR
MALARIA IFA TEST
Antigen: washed cell thick smears of RBCs infected with one species
- P. falciparum
- P. malariae
- P. ovale
- P. vivax
MALARIA IFA TEST
- Sensitivity 89/92 = 98%
- Based on Pv and Pf infections
- Specificity 1/184 = 99.5%
- Babesia may cross-react
MALARIA IFA TEST
Human Experimental Infections
- Parasitemia preceeds antibody
- P. falciparum 4-6 days
- P. vivax 2-6 days
- P. malariae 4-6 days
- If parasitemia is suppressed, may still develop detectable antibody
MALARIA IFA TEST
Antibody Persistence Post-Rx
Typical Malaria IFA Results
| Slide Diagnosis | P. falcip | IFA P. malariae |
P. ovale | P. vivax |
|---|---|---|---|---|
| P. falciparum | 1:16384 | 1:4096 | 1:1024 | 1:64 |
| P. falciparum | 1:1024 | Neg | Neg | Neg |
| P. ovale | Neg | Neg | 1:256 | Neg |
| P. vivax | Neg | Neg | 1:64 | 1:1024 |
| P. malariae | 1:1024 | 1:1024 | 1:64 | 1:64 |
CDC PCR FOR MALARIA
Two-step nested PCR
- Genus-specific primers followed by
- Species-specific primers (Snounou et al, 1993)
CDC PCR FOR MALARIA
Sensitivity & Specificity
100%+
based on smear results
ALGORITHM FOR LABORATORY TESTING OF SUSPECT DONORS
- Screen with serology
- PCR on IFA positives
- Blood film examination on IFA positives
TRANSFUSION TRANSMITTED MALARIA, 1963-1998
How 65 implicated donors were identified
TRANSFUSION TRANSMITTED MALARIA, 1963-1998
In implicated donors, where information was available:
- 98% had positive serology
- 33% had positive blood smear
Laboratory investigation of blood donors, 1996-2005
| Year | Species | Donors | IFA + | PCR + |
|---|---|---|---|---|
| 1996 | Falcip | 7 | 1 | 1 |
| 1998 | Falcip | 4 | 1 | 1 |
| 2002 | Malariae | 10 | 1 | 0 |
| 2003 | Falcip | 2 | 1 | 0 |
| 2005 | Falcip | 150 | 1/100 | 0 |
Laboratory investigation of blood donors, 1996-2005
| Year | Tx date | Spec date | Slide result | PCR result |
|---|---|---|---|---|
| 1996 | 11/12/96 | 3/1997 | Pos | Pos |
| 1998 | 1/15/98 | ?1/15/98 | Neg | Pos |
| 2002 | 5/1/02 | 7/11/02 | Neg | Neg |
| 2003 | 3/1/03 | 4/03 | Neg | Neg |
| 2005 | 6/30/05 | 8/29/05 | Neg | Neg |
Detection of Parasites/Parasite Products
Detection of Parasites/Parasite Products
Selected References
IFA
- Collins et al, Amer J Trop Med Hyg 1964;13:256
- Collins et al, Amer J Trop Med Hyg 1964;13:777
- Sulzer et al, Amer J Trop Med Hyg 1969;18:199
- Wilson et al, Amer J Trop Med Hyg 1970;19:401 Gleason et al, Amer J Trop Med Hyg 1971;20:10
PCR
- Snounou et al, Mol Biochem Parasitol 1993;61:315
- Johnston et al, J Clin Microbiol 2006;44:1087