Bulletin of the World Health Organization

A point-of-care test for measles diagnosis: detection of measles-specific IgM antibodies and viral nucleic acid

Lenesha Warrener, Rimantas Slibinskas, Kaw Bing Chua, Wondatir Nigatu, Kevin E Brown, Kestutis Sasnauskas, Dhanraj Samuel & David Brown

Volume 89, Number 9, September 2011, 675-682

Table 4. Results of polymerase chain reaction (PCR) and IgM antibody testing obtained for 24 oral fluid (OF) specimens used to compare viral nucleic acid recovery from OF aliquots and from used point-of-care test (POCT) strips

SN Real-time H-gene PCR result and viral strain
IgM antibody
OF aliquot POCT strip Surveillance POCT OF EIA
H (Ct) Strain H (Ct) Strain H (Ct) Strain Result T/COa
1 36.43 D4-a 35.88 D4-a 34.58 D4-a Pos Pos 19.57
2 30.72 D4-b 29.48 D4-b 30.37 D4-b Pos Pos 30.09
3 36.64 ND A ND NT Neg Neg 0.41
4 ND ND A ND NT Neg Neg 0.57
5 25.16 D4-c 27.62 D4-c 21.07 D4-c Pos Pos 5.54
6 30.69 D9 32.24 D9 30.08 D9 Pos Pos 17.52
7 34.89 D4-c 35.01 D4-c 31.57 D4-c Pos Pos 25.40
8 34.23 D4-c 35.12 D4-c 30.29 D4-c Pos Pos 23.63
9 ND ND A ND NT Pos Pos 1.22
10 33.20 D4-c 33.28 D4-c 30.34 D4-c Pos Pos 8.32
11 32.40 D4-d 33.53 D4-d 30.29 D4-d Pos Pos 19.57
12 26.85 D4-d 27.91 D4-d 23.21 D4-d Pos Pos 1.09
13 ND ND ND NT Pos Eqv 0.99
14 ND ND ND NT Neg Neg 0.58
15 ND ND ND NT Neg Neg 0.76
16 30.91 D4-c 28.26 D4-c 23.09 D4-c Pos Pos 9.74
17 31.88 D4-c 31.76 D4-c 30.02 D4-c Pos Pos 10.78
18 ND ND A ND NT Neg Neg 0.72
19 32.51 D4-b 33.32 D4-b 30.82 D4-b Neg Pos 27.74
20 ND D4-c ND D4-c 37.50 D4-c Pos Pos 19.04
21 31.23 D4-c 31.86 D4-c 32.34 D4-c Pos Pos 15.67
22 34.07 D4-e 33.99 D4-e 33.16 D4-e Pos Pos 17.14
23 37.32 34.34 A 37.41 Vaccine Pos Pos 23.25
24 ND ND ND NT Pos Pos 1.11

Ct, threshold cycle number; Eqv, equivocal; H, haemagglutinin; ND, not detected; Neg, negative; NT, not tested; Pos, positive; SN, specimen number.

a This represents the quotient calculated by dividing the optical density obtained for each test specimen (450/620 nm) by the cut-off value.

Note: The Ct obtained for the OF aliquots submitted for this evaluation, from POCT strips used in IgM antibody detection and from each oral fluid during routine surveillance testing, are listed. During routine surveillance testing, nested N-gene PCR and nucleic acid sequence analysis were only performed on oral fluids in which the H gene had been detected by real-time PCR. For this evaluation, real-time H-gene PCR, nested nucleocapsid-gene (N-gene) PCR and sequence analysis were performed on all 24 OF aliquots and their corresponding POCT strips. The measles virus strain designations listed are based on sequence analysis of nested PCR N-gene amplicons. Five different D4 measles virus strains were identified and each was assigned a different letter in the table: a, b, c, d, e. Strains b, c and d were obtained from more than one subject. Nested N-gene PCR negative results are indicated as –-.