The document proposes a pooled testing strategy called the 5-95 scheme to increase COVID-19 testing capacity in low-resource countries. It involves triaging samples as potentially positive or negative, pooling samples in a ratio of 5 potentially positive to 95 potentially negative, testing the pooled samples, and then testing individual samples from positive pools to identify positive cases. Simulation results show this approach can save up to 73 tests per 100 samples tested compared to individual testing, depending on disease prevalence. The method provides a cost-effective solution to expand limited testing in low-resource settings.

1. A recommendation for
COVID-19 TESTING in LOW-
RESOURCE COUNTRIES
Salvador Eugenio Caoili, MD, PhD, Ruby Anne King, MD, PhD,
Cecile Dungog, MD, PhD, John Carlo Reyes, MD, PhD,
Jesus Sarol, PhD and Romulo de Castro, PhD
April 2020

2. WHO TO TEST?
Pooled testing strategy could provide increased testing
capacity to accomplish Expanded Testing for COVID-19.
Based on DOH Department Memorandum No. 2020-0151 “Interim
Guidelines on Expanded Testing for COVID-19”, Released April 8, 2020
1. Suspect cases
2. Individuals with relevant history of travel and
exposure (or contact), whether symptomatic or
asymptomatic
3. Healthcare workers with possible exposure, whether
symptomatic or asymptomatic

3. Dorfman’s Pooled Testing Method
Dorfman, R. (1943). The detection of defective members of large populations. Ann Math Stat, 14(4), 436-440.
1. Pool individual samples (circles).
2. Test master pool (hexagon):
A. If the master pool will test negative,
and all individual samples are
negative → no further testing will be
needed.
B. If the master pool will test positive
(e.g., at least 1 the individual samples
is positive), individual sample testing
will be performed to determine this
positive sample.

4. Bharti, A. R., Letendre, S. L., Patra, K. P., Vinetz, J. M., & Smith, D. M. (2009). Malaria diagnosis by a polymerase chain reaction-based
assay using a pooling strategy. Am J Trop Med Hyg, 81(5), 754-757.
LEGEND
1. Test master pools 2X for higher sensitivity
○ If both (-): no need to proceed, all are (-)
○ If one is (+): proceed to #2
2. Test mini-pools (1-10 and A-J)
○ Note suspected (+) individuals in BOTH
vertical and horizontal mini-pools
3. Test suspected individuals identified in #2

5. Triage Samples
potentially positive potentially negative
5 potentially POSITIVE
95 potentially NEGATIVE
Artificially create 5% prevalence in sample population to save on tests.
Pool with
the 5-95 scheme

6. 5-95 SCHEME (n = 10)
5 individuals are positive (black circles) in 100
n: number of samples in a mini-pool
2 master pool
20 mini pools
12 individual samples
34 tests
SAMPLE SCENARIO
savings: 66 tests
no pooling
with pooling
100 tests

7. Prevalence
(f)
Savings
(No. of tests saved)
1% 77
2% 74 - 76
3% 69 - 75
4% 62 - 74
5% 53 - 73
6% 42 - 72
7% 29 - 71
8% 14 - 70
SAMPLE SCENARIO
10x10 matrix simulation for
different prevalence values (f)
100 specimens
n = 10
5-95 scheme could
save up to 73 tests
per 100 specimens

8. https://www.technion.ac.il/en/2020/03/pooling-method-for-accelerated-testing-of-covid-19/
POOLING
METHOD FOR
ACCELERATED
TESTING OF
COVID-19

9. Pool size (n) No. of Tests Needed No. of Tests Saved Percent Savings
3 47596 52404 52.4%
4 43549 56451 56.5%
5 42622 57378 57.4%
6 43157 56843 56.8%
8 46158 53842 53.8%
10 50126 49874 49.9%
12 54297 45703 45.7%
15 60338 39662 39.7%
20 69151 30849 30.8%
EFFECT OF POOL SIZE
Calculations for 100,000 specimens
Test sensitivity = 1.000 Prevalence = 5%

10. Pool size (n) Percent Savings
Sn = 1.000 Sn = 0.800
3 52.4% 55.1%
4 56.5% 59.5%
5 57.4% 61.5%
6 56.8% 61.6%
8 53.8% 59.6%
10 49.9% 56.5%
12 45.7% 52.9%
15 39.7% 57.5%
20 30.8% 39.2%
Calculations for 100,000 specimens
Prevalence = 5%EFFECT OF LOWERED SENSITIVITY

11. 1. Triage samples as potentially negative or potentially positive according to patient
symptoms.
2. Take 95 potentially negative and 5 potentially positive samples to comprise a 5-95
set up of 100 samples.
3. Pool the samples according to the scheme in slide 3 and create a master pool from the
entire population.
4. Test the master pool 2X:
4A. If both results are negative, then all 100 samples are negative → end.
4B. If at least 1 result is positive, continue to test mini-pools.
5. Test the 10 horizontal mini pools (A-J) and 10 vertical mini-pools (1-10). Note
individuals with positive vertical and horizontal mini-pools (suspected individuals).
6. Test the suspected individual samples to confirm.
PROTOCOL FOR THE 5-95 SCHEME

12. 1. Bharti, A. R., Letendre, S. L., Patra, K. P., Vinetz, J. M., & Smith, D. M. (2009). Malaria diagnosis by a
polymerase chain reaction-based assay using a pooling strategy. Am J Trop Med Hyg, 81(5), 754-
757.
2. Department of Health Philippines (2020) Revised administrative order no. 2020-0012 “Guidelines for
the inclusion of the coronavirus disease 2019 (COVID-19) in the list of notifiable diseases for
mandatory reporting to the Department of Health dated March 17, 2020. Retrieved April 15, 2020
from: https://bit.ly/COVID19AO2020-
0013?fbclid=IwAR1nlM8wAp8rRv4m6D_lwdTbMKRiYybDdYEMX0ppPmYmggipSH-8kk8VAME.
3. Department of Health Philippines (2020) Interim Guidelines on Expanded Testing for COVID-19.
Retrieved April 15, 2020.
4. Dorfman, R. (1943). The detection of defective members of large populations. Ann Math Stat, 14(4),
436-440.
5. Technion-Israel Institute of Technology. (2020). Pooling method for accelerated testing of COVID-19.
Retrieved from: https://www.technion.ac.il/en/2020/03/pooling-method-for-accelerated-testing-of-
covid-19/.
REFERENCES