Results

Post-mortem interval

Samples from 32 of the 53 adult spleens (60%) and all of the pediatric spleens could be punched. All punched samples could be biomechanically tested. The G’’ showed a significant negative correlation with the PMI (P(r) = -0.551; p = 0.002; Fig. 2). G’ (P(r) = -0.238, p = 0.200) and G* (P(r) = -0.286, p = 0.130) were not significantly correlated with the PMI. Hence, Receiver Operating Characteristic (ROC) curves were calculated only for the G’’ in 50-hour steps for PMI thresholds of 100 to 300 h. For the G’’ cut-off value with the highest calculated positive likelihood ratio, the results are depicted in Table 1 for PMI sub-group. The data of the 200-h group is depicted in detail in Fig. 3 as this was the PMI threshold with the highest positive likelihood ratio of all investigated sub-groups.

Fig. 2: The significant negative correlation between the loss modulus (G’’) and the post-mortem (PMI) interval is shown

PMI < [h] | AUC | Cut-off value [Pa] | Se [%] | 95% CI[%] | Sp [%] | 95% CI[%] | LR+
100 | 0.717 | > 479 | 33 | 5.9–70.0 | 96 | 79.0–99.8 | 7.67
150 | 0.773 | > 479 | 38 | 13.7–69.4 | 95 | 78.2–99.8 | 8.25
200 | 0.831 | > 333 | 75 | 46.8–91.1 | 94 | 73.0–99.7 | 12.75
250 | 0.692 | > 333 | 56 | 33.7–75.4 | 92 | 64.6–99.6 | 6.67
300 | 0.613 | > 309 | 50 | 31.3–68.6 | 80 | 37.6–99.0 | 2.50

Fig. 3: The data for the 200-h cut-off of the loss modulus (G’’) is depicted. (A) The G’’ values are shown as a scatter plot with the horizontal line representing the median. Values above median are only reached below 200 h. (B) The Receiver Operating Characteristic (ROC) curve is depicted

Age at death, spleen weight, sex, and cardiac resuscitation

None of the measured rheological properties was significantly correlated with age (G’: P(r) = -0.112; p = 0.540; G’’: S(r) = -0.272; p = 0.130; G*: P(r) = -0.141; p = 0.440) or spleen weight at autopsy (G’: P(r) = -0.178; p = 0.920; G’’: S(r) = -0.156; p = 0.400; G*: P(r) = -0.069; p = 0.710). None of the rheological properties differed significantly between males and females (Welch’s test; G’: t(10.39) = 0.59, p = 0.568; G’’: t(20.66) = 0.99, p = 0.334; G*: t(10.60) = 0.47, p = 0.651) and whether a cardiac resuscitation had been performed (Welch’s test; G’: t(26.49) = 0.51, p = 0.613; G’’: t(28.23) = 0.95, p = 0.348; G*: t(27.01) = 0.35, p = 0.732). An overview of the age at death, spleen weight, sex and PMI as well as the mean G’, G’’ and G* values of all here tested sub-groups is given in Table 2.

Group | Age at death [y] | Spleen weight [g] | Sex [f: m] | Samples | PMI [h] | G’ [Pa] | G’’ [Pa] | G* [Pa]
Females | 71 | 123 | - | 14 | 214 | 1148 | 294 | 1187
Males | 58 | 200 | - | 39 | 206 | 1053 | 337 | 1110
Mechanics group | 61 | 175 | 9:23 | 32 | 209 | 1080 | 325 | 1131
No mechanics group | 67 | 213 | 5:16 | 21 | 209 | - | - | -
With inflammation | 68 | 244 | 2:4 | 6 | 282 | 881 | 219 | 908
Without inflammation | 60 | 165 | 6:16 | 22 | 184 | 1115 | 350 | 1182
Mild fibrosis | 59 | 223 | 2:18 | 20 | 220 | 1044 | 289 | 1086
Severe fibrosis | 65 | 106 | 3:3 | 6 | 189 | 1019 | 391 | 1121
With blood congestion | 63 | 190 | 5:12 | 17 | 194 | 1128 | 347 | 1198
Without blood congestion | 60 | 169 | 3:8 | 11 | 224 | 967 | 284 | 1010
With resuscitation | 60 | 186 | 3:11 | 14 | 233 | 1111 | 315 | 1158
Without resuscitation | 64 | 161 | 5:11 | 16 | 177 | 1052 | 343 | 1110