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Table 2 Theoretical sensitivity of thick and thin blood films of surveyed laboratories (n = 50, MD = 27)

From: Malaria diagnosis in a malaria non-endemic high-resource country: high variation of diagnostic strategy in clinical laboratories in the Netherlands

Guideline/laboratory

Total magnification (ocular × objective)

Thick film

Thin film

Volume of thick film

Diameter of thick film

Number of fields examined

Theoretical total examined volume

Theoretical limit of detection (based on 2 trophozoites)

Theoretical fields examined

Theoretical total examined volume

Theoretical part of volume examined compared to thick film

Guideline

*

µL

mm

Number

µL

Trophozoites

/µL

Number

µL

%

NVP [9, 12]

1000

6

12

200

0.3

7.41

ND

  

BSH [10]

1000^

Several drops

–

200

  

ND

  

CDC [11]

1000^

Small drop

17.9**

100–300

  

–

  

WHO [8]

1000

6

12

100

0.1

14.29

ND

  

Range

         

 Minimum

500

6

6

75

0.09

1.2

40

0.002

0.8%

 Maximum

1250

15

23.25*

413

1.65

21.9

600

0.056

10.3%

 Mean

NA

8

14

207

0.47

7.4

190

0.010

3.4%

 Median

NA

6

13

200

0.31

6.5

175

0.009

2.9%

Laboratory

         

 A

1000

6

20

188

0.09

21.9

188

0.009

10.3%

 B

1000

–

–

   

263

0.013

 

 C

500

6

15

175

0.60

3.3

175

0.018

2.9%

 D

1000

6

6

200

1.08

1.9

ND

  

 E

1000

–

–

   

338

0.017

 

 F

625

–

–

   

113

0.009

 

 G

500

–

–

   

188

0.019

 

 H

1000

–

–

   

188

0.009

 

 I

1000

6

13

225

0.26

7.7

ND

  

 J

1000

–

10

   

75

0.004

 

 K

1000

–

–

   

275

0.014

 

 L

1250

6

13

338

0.31

6.5

74

0.003

1.0%

 M

1000

6

15

200

0.17

11.6

200

0.010

5.8%

 N

1000

6

13

188

0.22

9.3

ND

  

 O

1000

–

–

   

263

0.013

 

 P

500

6

15

338

1.17

1.7

563

0.056

4.8%

 Q

500

6

13

225

1.04

1.9

–

  

 R

500

–

–

   

125

0.006

 

 S

625

–

–

   

413

0.009

 

 T

1000

6

12

200

0.27

7.4

ND

  

 U

1000

–

–

   

40

0.002

 

 V

1000

6

11

200

0.32

6.2

ND

  

 W

1000

10

23.25

200

0.12

16.7

75

0.004

3.1%

 X

1000

6

12

200

0.27

7.4

ND

  

 Y

1000

–

–

   

113

0.006

 

 Z

1000

10

9

413

1.65

1.2

413

0.021

1.3%

 AA

1000

–

–

   

75

0.004

 

 AB

1000

6

–

   

49

0.002

 

 AC

1000

–

20

   

263

0.013

 

 AD

1000

–

–

   

113

0.006

 

 AE

1000

–

–

   

263

0.013

 

 AF

1000

6

12

200

0.27

7.4

–

  

 AG

1000

–

15

   

49

0.002

 

 AH

1000

–

–

   

263

0.013

 

 AI

1000

15

14

135

0.33

6.0

135

0.007

2.0%

 AJ

1000

–

–

   

338

0.017

 

 AK

1000

–

–

   

175

0.009

 

 AL

1000

–

–

   

74

0.004

 

 AM

1000

–

–

   

200

0.010

 

 AN

1000

6

12

113

0.15

13.2

ND

  

 AO

1000

6

10

200

0.39

5.1

200

0.010

2.6%

 AP

1000

6

–

   

75

0.004

 

 AQ

1000

6

–

   

600

0.030

 

 AR

1000

–

–

   

75

0.004

 

 AS

625

15

16

75

0.45

4.4

ND

  

 AT

1000

–

–

   

188

0.009

 

 AU

1000

15

–

   

74

0.004

 

 AV

1000

6

10

225

0.44

4.6

74

0.004

0.8%

 AW

1000

12

15

113

0.19

10.3

113

0.006

2.9%

 AX

1000

–

–

   

113

0.006

 
  1. –: missing data; .: no calculation possible due to missing data; ND: not determined for the detection of parasites; NA: not applicable
  2. *The size of 1 euro coin
  3. **The size of a US dollar dime
  4. ^1000× magnification and FN 18 of the ocular is assumed, based on the use of a 100× objective
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Malaria Journal

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