TABLE 3.

Association of stool specimen transport conditions and modified stool processing on the rate of errors associated with filter blockage and/or fluid transfer and on the MTB-positivity rate^a

Experiment	No. of aliquots			Association with errors related to filter blockage/fluid transferb		Association with MTB-positivityc
	Processed and tested	With valid result	With MTB detectedc	Univariable or (95% CI)	Multilevel or (95% CI)§	Univariable or (95% CI)	Multilevel or (95% CI)§
A1. Stool vol				18.7 (4.93–70.7)¶		0.7 (0.19–2.2)¶	0.6 (0.08–4.9)¶, ¶¶
0.3 g	81£	77	73	0.61 (0.14–2.63)		1.59 (0.43–5.87)
0.5 g	84	80	74	0.19 (0.02–1.67)		1.07 (0.33–3.48)
0.8 g	84	75	69	1 (REF)		1 (REF)
1.0 g	84	69	63	2.89 (0.98–8.52)		0.91 (0.28–2.98)
1.2 g	84	64	59	4.01 (1.4–11.44)		1.03 (0.3–3.53)
A2. Mixing stool and SR
Handshaking	123	110	101	1 (REF)	1 (REF)¶¶	1 (REF)
Vortexing	123	104	97	1.52 (0.68–3.43)	1.86 (0.68–5.12)	1.23 (0.44–3.45)
A3. Sedimentation time
5 min	123	110	101	1 (REF)	1 (REF)¶¶	1 (REF)
10 min	123	109	101	0.8 (0.32–2.01)	0.73 (0.24–2.2)	1.13 (0.42–3.03)
20 min	118∞	102	95	1.26 (0.54–2.94)	1.51 (0.54–4.23)	1.21 (0.43–3.38)
A4. Storage of stool/SR mixture‡
Direct testing (no storage)	122	111	102	1 (REF)	1 (REF)¶¶	1 (REF)
Fridge
5 h	122	108	100	1 (0.38–2.61)	1 (0.35–2.89)	1.1 (0.41–2.97)
12 h	122	104	99	1.5 (0.62–3.65)	1.66 (0.61–4.48)	1.75 (0.57–5.4)
24 h	122	100	94	2.03 (0.87–4.76)	2.46 (0.94 - 6.42)	1.38 (0.47–4.03)
Room temp
5 h	122	91	84	2.46 (1.07–5.65)	3.17 (1.24 - 8.13)	1.06 (0.38–2.96)
12 h	122	93	90	2.46 (1.07–5.65)	3.17 (1.24 - 8.13)	2.65 (0.7–10.08)
24 h	122	90	88	2.61 (1.14–5.96)	3.43 (1.35 - 8.76)	3.88 (0.82–18.45)
B. Stool specimen transport conditions†
No simulated transport	83	78	72	1 (REF)	1 (REF)	1 (REF)
Fridge
48 h	83	75	68	1.27 (0.33–4.89)	1.32 (0.31–5.67)	0.81 (0.26–2.53)
72 h	83	73	66	2.11 (0.61–7.28)	2.44 (0.63–9.43)	0.79 (0.25–2.46)
120 h	83	74	69	1.54 (0.42–5.66)	1.66 (0.4–6.83)	1.15 (0.34–3.94)
240 h	83	73	69	1.54 (0.42–5.66)	1.66 (0.4–6.83)	1.44 (0.39–5.31)
Room temp
48 h	83	63	60	5.45 (1.76–16.9)	8.45 (2.42–29.5)	1.67 (0.4–6.95)
72 h	83	71	68	2.7 (0.81–8.99)	3.34 (0.9–12.4)	1.89 (0.45–7.85)
120 h	83	68	67	4 (1.26–12.7)	5.57 (1.56–19.9)	5.58 (0.65–47.6)
240 h	83	64	59	4.71 (1.5–14.7)	6.92 (1.96–24.4)	0.98 (0.29–3.38)
Incubator
48 h	83	65	63	4.35 (1.38–13.7)	6.22 (1.76–22.1)	2.63 (0.51–13.47)
72 h	83	59	57	5.85 (1.89–18)	9.3 (2.67–32.3)	2.38 (0.46–12.21)
120 h	83	62	61	4.35 (1.38–13.7)	6.22 (1.76–22.1)	5.08 (0.6–43.39)
240 h	83	60	58	6.25 (2.03–19.2)	10.2 (2.94–35.3)	2.42 (0.47–12.42)

^aMultilevel analyses are displayed if these models performed better than the crude models. †, conditions after receipt at NTRL, so excluding the conditions occurring between stool collection and receipt at the NTRL; §, multilevel logistic regression analysis, including two levels as results were considered to be correlated within participants and stools, unless otherwise indicated; ¶, shows the trend per step of 0.2 g. Multilevel logistic regression analysis, including two levels as results were considered to be correlated within stools within participants; ¶¶, multilevel logistic regression analysis, including one level as results showed to be correlated within participants, but not within stools of the same participant; £, 3 samples were used for an early experiment with 1.5 g of stool; ∞, 5 aliquots were used for an early “no sedimentation” experiment.

^bThese are errors 2008, 5006, 5007, and 5017, which may be related to stool processing, as these may be caused by debris clogging the cartridge filter (2008) or disturbing the fluid transfer within the cartridge (5006, 5007, and 5017).

^cMTB positivity defined as trace call or higher.