Severe Plasmodium vivax Malaria in Pakistan Ali Bin Sarwar Zubairi, Sobia Nizami, Afsheen Raza, Vikram Mehraj, Anita Fazal Rasheed, Najia Karim Ghanchi, Zahra Nur Khaled, and M. Asim Beg To compare the severity of Plasmodium vivax malaria with that of P. falciparum malaria, we conducted a retrospec- tive cross-sectional study of 356 adults hospitalized with malaria (2009–2011) in Pakistan. P. vivax and P. falciparum accounted for 83% and 13% of cases, respectively; 79.9% of patients with severe malaria were infected with P. vivax. M alaria is endemic to Pakistan and 64% and 36% of malaria cases are attributed to Plasmodium vivax and P. falciparum, respectively (1). The purpose of this study was to identify the complications of P. vivax among hos- pitalized malaria patients and compare the prevalence of these complications with those of P. falciparum malaria. The Study We conducted a retrospective cross-sectional study using convenience sampling at the Aga Khan University Hospital in Karachi, Pakistan. Participants were all adult patients (>16 years of age) who were hospitalized with malaria during January 2009–December 2011. Reasons for hospitalization included intravenous antimalarial therapy, management of associated diagnoses, and complications. The following data on patients were retrieved through the hospital’s electronic and ile records: age, sex, infecting Plasmodium species, malaria diagnosis methods, co-exist- ing conditions, results of biochemical and microbiological investigations, radiographic indings, complications, hospi- tal course, and outcome. Records showed that Giemsa-stained peripheral blood smears, the malaria rapid diagnostic test (RDT), or both, were used for malaria diagnosis. The RDT used antibodies against P. falciparum histidine-rich protein 2 and P. vivax lactate dehydrogenase. For 45 case-patients for which re- sults from peripheral blood smears and RDTs were discor- dant or unreliable, surface protein-speciic PCR was per- formed by using stored patient blood samples to identify the Plasmodium species (2,3). Clinical syndromes were classiied as severe on the basis of the World Health Orga- nization’s 2010 severe falciparum malaria criteria (4). Statistical analysis was performed by using SPSS version 20 (http://www-01.ibm.com/software/analytics/ spss/). Averages, χ 2 test of independence, odds ratios with 95% CIs, and analysis of variance were computed when applicable. Case-patients with prior co-morbid conditions were excluded from relevant subanalyses, for example, diabetes mellitus patients were excluded from hypoglycemia analy- sis. All analysis was also repeated after excluding all case- patients with associated infections and comorbid illnesses. The classiication “comorbidity” included all conditions in the Charlson comorbidity index for mortality (5). The study was approved by the Aga Khan University’s Ethics Review Committee. A total of 356 patients with malaria (mean ± SD age 42 ± 18 years) were hospitalized in the Aga Khan Hospital during 2009–2011. Among these, 296 (83.1%), 47 (13.2%), and 13 (3.7%) were found to have P. vivax infection, P. fal- ciparum infection, and mixed infections ( P. vivax and P. falciparum), respectively. Baseline patient demographics are given in Table 1. The proportion of P. vivax infection among hospitalized malaria patients increased from 75.0% in 2009 to 87.7% in 2011 (p<0.02) (Figure 1, panel A). One hundred thirty-nine (39.0%) patients had at least 1 complication by World Health Organization criteria (4), among which 111 (79.9%) patients had P. vivax infection. In 24 (51.0%) cases of P. falciparum infections and in 111 cases (37.5%) of P. vivax infections, respectively, severe malaria developed (p = 0.077). As shown in Figure 2, the proportion of severe malaria among P. vivax patients in- creased from 24.1% in 2009 to 43.2% in 2010 and 39.5% in 2011 (p = 0.02). The most common complications in the patients are shown in Table 2. P. vivax and P. falciparum were respon- sible for comparable rates of pulmonary edema, the need for mechanical ventilation, coagulopathy, hypoglycemia, hemoglobinuria, metabolic acidosis, renal impairment, liver dysfunction, bleeding, and multi-organ dysfunction. Altered consciousness, anemia, and jaundice were associ- ated with P. falciparum malaria. The mean platelet count for P. vivax patients was 55, signiicantly lower than that of P. falciparum patients (67.5; p = 0.001) and those with mixed infections (61; p = 0.024). The mean hospital stay was 4.1 days for P. falciparum patients, 3.6 days for P. vivax patients, and 2.9 days for patients with mixed infections. Three P. vivax malaria pa- tients experienced fatal acute myocardial infarctions. One patient, who had metastatic myeloma and P. falciparum malaria, died. The mortality rate was 2.1% for P. falci- parum patients and 1.0% for P. vivax patients (p = 0.50). Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 19, No. 11, November 2013 1851 Author afiliations: Aga Khan University, Karachi, Pakistan (A.B.S. Zubairi, S. Nizami, A. Raza, A.F. Rasheed, N.K. Ghanchi, Z.N. Khaled, M.A. Beg); and Aix Marseille Université, Marseille, France (V. Mehraj) DOI: http://dx.doi.org/10.3201/eid1911.130495