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EARNING

BOUT

EACTOR

RID

VALUATION

(SYPHILIS)

Schaffzin JK, Koumans EH, Kahn RH, Markowitz LE. Evaluation of syphilis reactor grids: optimizing impact.Sexually Transmitted Diseases 2003;30(9):700-706.

LARGE

• Reactor grids

• Methods for reactor grid evaluation

• Results

• Conclusions

Syphilis reactor grids

40

50

60

70

20

32168421WR

30

STS Lab ResultsA

ge

Gro

up

s

CLOSED

OPEN


40

50

60

70

20

32168421WR

30

STS Lab ResultsA

ge

Gro

up

s

CLOSED


40

50

60

70

20

32168421WR

30

STS Lab ResultsA

ge

Gro

up

s

70

60

50

40

20

32168421WR

30

VARIABLE AREA

Objectives

1. Evaluate the effect different grids and different prevalences have on:

2. Identify characteristics of cases not investigated by grid design

- Missed cases

- Investigations that yield no cases

Reactor grid evaluation

1. Identify population groups of reactors with different prevalence of syphilis, all of whom were investigated with known outcome and none of whom were applied to any grids

2. Select five grids representing the range of currently used grids

3. Apply groups of reactors to these five grids

Methods for grid evaluationsteps

• 5 jail surveillance projects (1999-2001)

• 1 mobile screening site (1999-2001)

• All people with reactive confirmed serologies had follow-up and staging

Selection of different population groups

Groups

Group D(SF + MA)

13,012 screened347 reactors

Group C*(Baton Rouge) 3,375 screened

196 reactors

Group B(Nashville)


Group A(Milwaukee)


New cases of syphilis

5

36

234

143

Prevalence among

reactors

1%

18%

28%

55%

Prevalence of syphilis by group

Reactor grids selected

Grid 5Grid 1

OPEN

CLOSED

NA

Age Trep R WR 1:1 1:2 1:4 1:8 1:16 ≥1:320-45-910-1415-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-74>74No Age



Grid 2


Grid 3


Grid 4


Grid 2


Grid 3


Grid 4

Applied to

Grids

Group A(Milwaukee)

55%

Group B(Nashville)

28%

Group C (Baton Rouge)

18%

Group D(SF + MA)

1%

Groups

Grid outcomeReactors closed

Grid 1

Grid 2

Grid 3

Grid 4

Grid 5

OPEN

CLOSED

Grid outcome

Most inclusive

Most exclusive

Percent of reactors closed

Groups A-D

0

10

20

30

40

50

60

70

80

90

100

A (55%) B (28%) C (18%) D (1%)

Group (prevalence)

% o

f re

acto

rs c

lose

d

Grid 1

Grid 2

Grid 3

Grid 4

Grid 5

Group A(Milwaukee)

55%

Group B(Nashville)

28%

Group C (Baton Rouge)

18%

Group D(SF + MA)

1%

Groups

Grid outcome, cases missed

OPEN

CLOSED

Grid outcome

Grid 1

Grid 2

Grid 3

Grid 4

Grid 5

Most inclusive

Most exclusive

“Cases Missed”

Cases

Non-Cases

Cases

Non-Cases

Case classification

Percent of syphilis cases not investigated

0

10

20

30

40

50

60

70

A (55%) B (28%) C (18%) D (1%)

Group (prevalence)

% o

f ca

ses

no

t in

vest

igat

ed

Grid 1

Grid 2

Grid 3

Grid 4

Grid 5

Groups A-D

Conclusions 1

Cases missed

• Percent of cases missed depends on grid design

“Non-cases investigated”

“Cases missed”

Open

Closed

Grid 1

Grid 2

Grid 3

Grid 4

Grid 5

Group A(Milwaukee)

55%

Group B(Nashville)

28%

Group C(Baton Rouge)

18%

Group D(SF & MA)

1%

Groups

Cases

Non-cases

Cases

Non-cases

Grid outcome

Case classification

Grid outcomes, non-cases investigated

Percent of non cases investigated

0

10

20

30

40

50

60

70

80

90

100

A (55%) B (28%) C (18%) D (1%)

Group

% o

f re

acto

rs in

vest

igat

ed w

ho

wer

e n

ot

case

s

Grid 1

Grid 2

Grid 3

Grid 4

Grid 5

Groups A-D

Conclusions 2

Investigations of non-cases

• Proportion of investigations that are not cases depends on prevalence of syphilis among reactors

• Investigations of non-cases are virtually independent of grid design

• Use of a grid doesn’t increase concentration of syphilis among investigated reactors

1111

86

255

14

1

54321Grid

1

222

2016

12

7

1

5421

Age Group

60-69

50-59

40-49

30-39

20-29

10-19

Grid

Female

2

7

3

Male

Age distribution of early cases missed

1

5

54

56

43

5

Total Cases

4912110421920Total 9164 145

0

2

16

83

42

2

Total Cases

• Cases excluded by age tend to be:

- Men ages 30-50

- Women ages 20-40

54321Grid

5421Grid

Female

3

Male

Titer distribution of early cases missed

31

1

1451

18101

31

32Titer

1:16

1:8

1:4

1:1-1:2

Trep only

WR

4

4

1

117

9

14

18

3

3

Total Cases

4912110421920Total 9164 145

1

1

19111

153

72

66

81

17

19

15

7

6

Total Cases

• Cases excluded tend to have:

- RPR titer 1:1 – 1:4

Overall conclusions

The percentage of cases missed by a grid is dependent on grid design.

The percentage of investigations that are not cases is dependent on prevalence of syphilis among reactors.

In areas with moderate to high prevalence (>10%), use of certain grids will lead to missed cases, whereas in low prevalence areas (<10%) grids can reduce the percentage of unnecessary investigations.

Implications

• Grid evaluation should include the following:

• Grids should be designed to minimize cases missed

• Percent of non-productive investigations should not be a focus of grid design

• Limited resources driving grid design can lead to missed cases

• As yet no guidance on what percentage of cases missed is “acceptable”

- Determination of grid design (inclusive vs. exclusive)

- Calculation of syphilis prevalence among reactors

Acknowledgements

CDC ATPM

Josh SchaffzinEmily Koumans Richard Kahn Lauri Markowitz

Catherine McLean Jim Braxton

Gabriela Paz-Bailey

Vera Schomer

Thanks to Charlotte Kent, Robert Kohn, Anne Spalding, Elizabeth Mangiamelli, Chris Freeman, Dacid Lundberg,

Josephine Ford Michael Whelan, Kathy Middleton, Mary Kay Schuknecht, John Thilges, Jim Braxton

Reactor Grid Evaluation

Late (%)

Early (%)Dx

Female (%)

Male (%)Gender

Mean

RangeAge

Reactors

0.6

0.9

101 (29)

246 (71)

23.1

18-62

347

Group E

NA

7

74 (58)

54 (42)

34.9

12-52

124

Group D

10

9

134 (68)

62 (32)

36.9

13-76

196

Group C

9

19

270 (32)

576 (68)

34.9

9-75

846

Group B

8

47

134 (51)

126 (49)

36.0

18-64

260

Group A

Group Demographics

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