title: Surmised total leucocyte counts miscalculate the parasite index of Plasmodium vivax malaria patients of tertiary and primary care settings in South-Western India.
abstract: BACKGROUND
  For the calculation of parasite index (PI) by microscopy method, an assumed total leucocyte count (TLC) of 8,000/μL is used conventionally. However, due to obvious variation in the population and individual TLCs, use of 8,000/μL may result in either over/underestimation of the PI.
  
  
  METHODS
  This study was aimed at ascertaining the utility of 8,000/μL TLC, as well as other assumed TLCs, with respect to measured TLC for the calculation of PI. A tertiary care hospital and five primary health centres were the base for the prospective study conducted among microscopically proven, symptomatic Plasmodium vivax mono-infection patients aged ≥18 years. PIs calculated by assumed TLCs ranging from 4,000-11,000/μL were compared with those calculated by measured TLCs. Geometric mean with 95% confidence interval, Bland-Altman plot and Wilcoxon signed rank test were used for statistical analysis.
  
  
  RESULTS
  A total of 284 P. vivax mono-infection patients, including 156 from a tertiary care hospital and 128 from five primary health centres, were recruited in the study. Assumed TLCs below 5,000 cell/μL and above 5,500 cell/μL in tertiary care setting resulted in significant (p <0.05) underestimation and overestimation, respectively. However, in primary health centres, it was an assumed TLC of 5,000 cell/μL, below and above which there was significant (p <0.05) underestimation and overestimation observed, respectively.
  
  
  CONCLUSIONS
  Assumed TLC of 8,000/μL is not suitable for the calculation of PI. Either actual TLC of the patient should be measured or a representative TLC should be derived for the population under investigation for any study requiring calculated PI by microscopy.
authors.affiliation: Department of Medicine, Kasturba Medical College, Manipal University, Manipal, Karnataka, India. rishikeshkumar@live.in.
authors.forename: Kumar
authors.initials: K
authors.lastname: Rishikesh
authors.affiliation: Department of Medicine, Kasturba Medical College, Manipal University, Manipal, Karnataka, India. sathishuppoor@yahoo.com.
authors.forename: Sathish Kitta
authors.initials: SK
authors.lastname: Madivala
authors.affiliation: Department of Medicine, Kasturba Medical College, Manipal University, Manipal, Karnataka, India. prashanthprabhu88@gmail.com.
authors.forename: Prashantha
authors.initials: P
authors.lastname: Prabhu
authors.affiliation: Department of Community Medicine, Kasturba Medical College, Manipal University, Manipal, Karnataka, India. aashakamat@gmail.com.
authors.forename: Asha
authors.initials: A
authors.lastname: Kamath
authors.affiliation: District Malaria Office, Udupi, Karnataka, India. dmoudp@yahoo.co.in.
authors.forename: Herikudru
authors.initials: H
authors.lastname: Ashok
authors.affiliation: Department of Medicine, Kasturba Medical College, Manipal University, Manipal, Karnataka, India. vsagar33@yahoo.com.
authors.forename: Sudha
authors.initials: S
authors.lastname: Vidyasagar
authors.affiliation: Department of Medicine, Kasturba Medical College, Manipal University, Manipal, Karnataka, India. shastryba@yahoo.co.in.
authors.forename: Ananthakrishna Barkur
authors.initials: AB
authors.lastname: Shastry
authors.affiliation: Department of Medicine, Kasturba Medical College, Manipal University, Manipal, Karnataka, India. kavithasaravu@gmail.com.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Saravu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007194:India / Q000453:epidemiology; D007958:Leukocyte Count; D016780:Malaria, Vivax / Q000175:diagnosis / Q000453:epidemiology* / Q000469:parasitology; D008297:Male; D008875:Middle Aged; D059208:Parasite Load / Q000379:methods*; D010966:Plasmodium vivax / Q000302:isolation & purification; D011446:Prospective Studies; D055815:Young Adult