WEBVTT 1 00:00:08.150 --> 00:00:09.500 First, I'm just going to review 2 00:00:09.500 --> 00:00:14.116 some basic strategies and clinical context for evaluating prolonged clotting times 3 00:00:14.116 --> 00:00:18.400 with a focus on prothrombin time and partial thrombolysis in time, 4 00:00:19.183 --> 00:00:22.183 an apt. 5 00:00:22.566 --> 00:00:26.466 There's a variety of different clinical scenarios when we might be asked 6 00:00:26.466 --> 00:00:30.100 to evaluate prolonged clotting times in the clinical laboratory. 7 00:00:30.350 --> 00:00:33.350 Sometimes it's an unexpected finding, 8 00:00:33.350 --> 00:00:37.116 an unexpected or incidentally identified clotting time prolongation. 9 00:00:37.566 --> 00:00:41.266 Sometimes patients are bleeding and their clotting times are prolonged 10 00:00:41.266 --> 00:00:44.800 in the first round of evaluating for a bleeding disorder. 11 00:00:45.500 --> 00:00:48.500 Sometimes the patient has personal or family history 12 00:00:48.733 --> 00:00:51.800 that leads the clinical team to suspect an acquired 13 00:00:51.800 --> 00:00:54.800 or inherited coagulation factor deficiency. 14 00:00:55.066 --> 00:00:58.266 And sometimes we're asked to use clotting times to help 15 00:00:58.266 --> 00:01:02.300 either monitor anticorps excellent therapy or evaluate 16 00:01:02.300 --> 00:01:06.100 an excessive prolongation for the given dose of an anticoagulant. 17 00:01:06.850 --> 00:01:09.350 Point being, there's a lot of different reasons why 18 00:01:09.350 --> 00:01:13.300 we might be curious about clotting time prolongation, 19 00:01:13.666 --> 00:01:18.516 and we might consider further evaluation in the Hemostasis Thrombosis Laboratory. 20 00:01:20.616 --> 00:01:23.666 It wouldn't be a colleague talk if I didn't show you the Cascades. 21 00:01:23.683 --> 00:01:26.566 Or let's just get that out of the way up front. 22 00:01:26.566 --> 00:01:31.666 This, of course, is a simplified way of thinking about hemostasis in patients, 23 00:01:31.666 --> 00:01:35.683 and particularly the part of hemostasis that we call secondary hemostasis. 24 00:01:36.366 --> 00:01:38.833 The series of enzymatic reactions that lead 25 00:01:38.833 --> 00:01:41.950 to production of fibrin monomers that eventually polymerize 26 00:01:42.233 --> 00:01:45.550 and really cement together the hemostatic plug. 27 00:01:46.716 --> 00:01:48.916 The cascade model is useful 28 00:01:48.916 --> 00:01:54.466 for thinking about the way the different factors contribute to clotting times, 29 00:01:54.466 --> 00:01:58.750 notably the prothrombin time and the partial thermoplastic in time. 30 00:01:59.050 --> 00:02:03.283 So, as is demonstrated here, the extrinsic 31 00:02:03.283 --> 00:02:07.450 pathway includes factor seven that's activated by tissue factor. 32 00:02:07.700 --> 00:02:10.566 And this is the mechanism of activation of coagulation 33 00:02:10.566 --> 00:02:12.616 measured by the reaction. 34 00:02:12.616 --> 00:02:17.350 And then continues on into the common pathway with eventual production of fibrin. 35 00:02:18.350 --> 00:02:19.700 The intrinsic pathway 36 00:02:19.700 --> 00:02:23.500 over here begins with negatively charged particles. 37 00:02:23.500 --> 00:02:24.850 In the clinical laboratory. 38 00:02:24.850 --> 00:02:29.083 That's often compounds like kaolin or silica that come in contact 39 00:02:29.083 --> 00:02:32.916 with the so-called contact factors to initiate coagulation 40 00:02:32.916 --> 00:02:36.016 through this pathway and then on down the common pathway. 41 00:02:36.250 --> 00:02:40.933 So the intrinsic pathway factors contribute to the PTT reaction. 42 00:02:41.383 --> 00:02:44.766 Having a solid understanding of the coagulation cascade 43 00:02:44.766 --> 00:02:48.316 can be very helpful in troubleshooting prolonged clotting times, 44 00:02:48.516 --> 00:02:54.433 and can help select appropriate follow up factor assays to help zero in on what 45 00:02:54.433 --> 00:02:57.950 the underlying cause of a clotting time prolongation might be. 46 00:02:58.400 --> 00:03:01.750 I’d just like to review what our differential diagnosis 47 00:03:01.750 --> 00:03:04.750 is for various prolonged clotting times. 48 00:03:04.983 --> 00:03:09.033 We'll start with the and then move on from there. 49 00:03:09.300 --> 00:03:13.000 So when I think about a patient who has an isolated, prolonged, 50 00:03:13.900 --> 00:03:17.950 but normal PTT, here are some of the things that come to mind. 51 00:03:18.150 --> 00:03:21.033 First and foremost, thinking back to the cascade, I'm 52 00:03:21.033 --> 00:03:24.450 thinking about a deficiency or a specific 53 00:03:24.450 --> 00:03:27.450 inhibitor directed against factor seven. 54 00:03:27.766 --> 00:03:33.400 Knowing that factor seven is in that extrinsic pathway that the RT measures. 55 00:03:34.050 --> 00:03:37.483 Other things I might be thinking about, in addition to problems 56 00:03:37.483 --> 00:03:41.200 with factor seven could include anticoagulant medications. 57 00:03:41.433 --> 00:03:46.383 Warfarin comes to mind as one that often prolongs the, as well 58 00:03:46.383 --> 00:03:51.033 as potentially DirectX ten inhibitors, although there's much more variation, 59 00:03:51.550 --> 00:03:55.950 in the response of the RT two direct RNA inhibitors, that varies quite a bit 60 00:03:55.950 --> 00:04:01.600 by the specific RT reagent, as well as the specific DirectX ten inhibitor drugs. 61 00:04:01.600 --> 00:04:06.516 So rivaroxaban, apixaban, edoxaban all have slightly different, 62 00:04:06.566 --> 00:04:11.733 different effects on RT that varies by reagent. 63 00:04:13.150 --> 00:04:13.983 Liver disease, 64 00:04:13.983 --> 00:04:19.116 particularly early may result in a prolonged RT before the RT prolongs 65 00:04:19.750 --> 00:04:22.750 and as well as vitamin K deficiency. 66 00:04:22.800 --> 00:04:25.683 Some cases of DIC, particularly early. 67 00:04:25.683 --> 00:04:29.433 And one thing that we are always thinking about in our laboratory is pre 68 00:04:29.433 --> 00:04:32.950 analytic variables that could contribute to prolonged clotting time. 69 00:04:32.950 --> 00:04:36.233 So this could include things like 70 00:04:37.566 --> 00:04:39.550 clotted specimens. 71 00:04:39.550 --> 00:04:42.550 This could include high hematocrit specimens 72 00:04:42.833 --> 00:04:45.733 that need to have citrate adjusted. 73 00:04:45.733 --> 00:04:50.650 This could include samples that have gone through uncontrolled freeze thaw cycles. 74 00:04:50.650 --> 00:04:55.133 So particularly in regards to factor seven there's a potential for cold activation 75 00:04:55.150 --> 00:04:58.566 of factor seven if it's gone through an uncontrolled freeze thaw cycle. 76 00:04:59.500 --> 00:05:03.283 So pre analytic variables are important to think about 77 00:05:03.283 --> 00:05:07.450 as potential spurious causes of prolonged clotting times 78 00:05:07.650 --> 00:05:10.833 that might not relate to some of these clinical indications. 79 00:05:10.833 --> 00:05:11.200 Here. 80 00:05:13.800 --> 00:05:15.783 When you think about prolonged clotting times, 81 00:05:15.783 --> 00:05:19.600 something that often comes to mind is lupus anticoagulant. 82 00:05:19.600 --> 00:05:21.150 And that will be an important part 83 00:05:21.150 --> 00:05:24.816 of our discussion of potential causes of prolonged PTT. 84 00:05:25.333 --> 00:05:29.883 But in general, most lupus anticoagulants don't tend to prolong the prothrombin 85 00:05:29.883 --> 00:05:33.733 time because of the very high amounts of forceful lipid in the reagent, 86 00:05:34.083 --> 00:05:37.083 except in rare cases of lupus anticoagulant 87 00:05:37.150 --> 00:05:40.833 with associated high proposed hypo prothrombin Amia. 88 00:05:41.316 --> 00:05:44.733 That's an unusual setting, where the antibodies are particularly directed 89 00:05:44.733 --> 00:05:47.850 against prothrombin and can be associated with clinical bleeding. 90 00:05:48.100 --> 00:05:51.450 It's a fascinating topic, but not where we're going to spend 91 00:05:51.900 --> 00:05:54.900 the main part of our energies today. 92 00:05:56.733 --> 00:05:58.083 Now, we mentioned that 93 00:05:58.083 --> 00:06:02.283 when we're thinking about a prolonged p t, we're considering 94 00:06:02.283 --> 00:06:06.850 potential factor deficiencies or factor inhibitors. 95 00:06:07.266 --> 00:06:12.066 And I just want to take a moment to review mixing studies as an important tool 96 00:06:12.066 --> 00:06:16.000 for helping us to determine whether a clotting time prolongation 97 00:06:16.000 --> 00:06:19.983 may be related to a factor deficiency or an inhibitor. 98 00:06:20.733 --> 00:06:22.383 So a quick review here. 99 00:06:22.383 --> 00:06:26.400 Mixing studies involve mixing platelet poor plasma from our patient 100 00:06:26.616 --> 00:06:29.616 with an equal volume in most cases, 101 00:06:29.733 --> 00:06:32.733 of normal pooled plasma. 102 00:06:33.000 --> 00:06:35.833 Both are platelet poor. We mix them together 103 00:06:35.833 --> 00:06:38.833 and measure the clotting time that was initially prolonged. 104 00:06:39.000 --> 00:06:41.883 Could be, as in our last slide. 105 00:06:41.883 --> 00:06:42.333 Could be. 106 00:06:43.483 --> 00:06:43.833 And we 107 00:06:43.833 --> 00:06:47.733 look to see does that mixture correct. 108 00:06:47.733 --> 00:06:52.116 Meaning the normal pool of plasma has supplied some factors that are missing 109 00:06:52.750 --> 00:06:55.233 suggesting a factor deficiency pattern. 110 00:06:55.233 --> 00:06:59.100 Or does the clotting time remain prolonged in the mixture, 111 00:06:59.166 --> 00:07:01.183 suggesting an inhibitor pattern. 112 00:07:01.183 --> 00:07:04.500 So even adding factors in from the normal pooled plasma 113 00:07:04.800 --> 00:07:07.800 is not sufficient to correct the clotting time. 114 00:07:07.933 --> 00:07:10.050 Again, 115 00:07:10.050 --> 00:07:12.283 definitions of correction can vary. 116 00:07:12.283 --> 00:07:14.916 Can vary from laboratory to laboratory. 117 00:07:14.916 --> 00:07:18.150 So each individual laboratory needs to select 118 00:07:18.150 --> 00:07:21.150 and validate its own definition of correction. 119 00:07:21.400 --> 00:07:24.550 But the general principles, are the same everywhere. 120 00:07:24.550 --> 00:07:28.100 We're looking for the ability of normal plasma to either correct 121 00:07:28.116 --> 00:07:33.400 a clotting time or looking to see if the clotting time remains prolonged 122 00:07:33.400 --> 00:07:38.616 after mix with a normal pool, suggesting an inhibitor pattern for the PTT. 123 00:07:38.616 --> 00:07:42.400 We know there are some time dependent inhibitors, so it's important to include 124 00:07:42.400 --> 00:07:46.416 an incubated mixing study step for the PTT reaction. 125 00:07:46.416 --> 00:07:47.316 Specifically. 126 00:07:49.833 --> 00:07:50.200 And when 127 00:07:50.200 --> 00:07:53.233 we look at non corrected mixing studies, the kinds of things 128 00:07:53.233 --> 00:07:56.616 we're thinking about are either specific factor inhibitors 129 00:07:57.216 --> 00:08:00.216 as a factor seven inhibitors we discussed with the 130 00:08:00.933 --> 00:08:04.233 or anticoagulants that can behave as inhibitors. 131 00:08:04.533 --> 00:08:09.633 In a mixing study for the reaction we're looking at specific inhibitors 132 00:08:09.633 --> 00:08:14.850 against intrinsic pathway factors, as well as anticoagulant medications 133 00:08:14.850 --> 00:08:19.350 that could act as inhibitors in the mixing study, and then lupus 134 00:08:19.383 --> 00:08:24.950 anticoagulant is another potential cause of an inhibitor pattern in the PTT. 135 00:08:24.966 --> 00:08:27.250 Particularly 136 00:08:27.250 --> 00:08:29.850 common pathway factor inhibitors tend to prolong 137 00:08:29.850 --> 00:08:33.783 both the PD and PTT and show an inhibitor or non 138 00:08:33.783 --> 00:08:37.933 correction pattern in mixing studies with both types of clotting times. 139 00:08:38.733 --> 00:08:43.416 We'll now turn our attention to the differential diagnosis of prolonged PTT. 140 00:08:44.100 --> 00:08:48.750 As we just mentioned we're thinking about problems with intrinsic pathway factors. 141 00:08:48.750 --> 00:08:54.300 So these could be deficiencies of factors eight 911 or contact factors 142 00:08:54.600 --> 00:08:58.083 or inhibitors directed against one of these factors. 143 00:08:58.083 --> 00:09:02.283 So again knowing the factors where they're placed in the coagulation 144 00:09:02.283 --> 00:09:03.516 cascade can help us 145 00:09:03.516 --> 00:09:07.333 to make predictions about potential causes for prolonged clotting times. 146 00:09:07.983 --> 00:09:10.333 Lupus anticoagulant is another important 147 00:09:10.333 --> 00:09:13.383 cause of AP prolongation, 148 00:09:13.800 --> 00:09:18.000 anticoagulant medications, heparin and direct thrombin inhibitors, 149 00:09:18.000 --> 00:09:22.500 most notably but others can also cause PTT prolongation. 150 00:09:23.283 --> 00:09:27.933 Elevated CRP or C-reactive protein can be a potential cause 151 00:09:27.933 --> 00:09:32.400 of prolonged PTT and some cases of von Willebrand disease. 152 00:09:32.400 --> 00:09:36.150 If the factor Ed activity is sufficiently low, so many cases of von 153 00:09:36.150 --> 00:09:40.266 Willebrand disease have mild deficits in factor eight activity 154 00:09:40.266 --> 00:09:42.483 that aren't sufficient to prolong the PTT, 155 00:09:42.483 --> 00:09:45.816 but there are a subset of cases where PTT may be prolonged. 156 00:09:46.183 --> 00:09:49.450 And then, as we mentioned in our discussion of the pre 157 00:09:49.450 --> 00:09:53.500 analytic variables, can lead to prolongation of the PTT also. 158 00:09:53.500 --> 00:09:57.066 And it's always important to consider those in our differential diagnosis. 159 00:09:59.733 --> 00:10:01.933 Now what do we think about if 160 00:10:01.933 --> 00:10:05.233 both the PD and PTT are prolonged. 161 00:10:06.216 --> 00:10:09.816 First thing that I turn my attention to our potential deficiencies 162 00:10:09.816 --> 00:10:14.583 are inhibitors, directed against common pathway factors 163 00:10:14.883 --> 00:10:18.666 so that are common to both the PD and PTT reactions. 164 00:10:19.300 --> 00:10:23.800 I'm also thinking about causes that can result in severe multiple factor 165 00:10:23.800 --> 00:10:26.683 deficiencies, things like severe liver disease, 166 00:10:26.683 --> 00:10:30.033 disseminated intravascular coagulation, or DIC, 167 00:10:30.450 --> 00:10:34.900 very high levels of anticoagulant, particularly high levels of warfarin 168 00:10:35.200 --> 00:10:39.816 or poisoning with the rodenticide superfriends are very severe 169 00:10:39.816 --> 00:10:41.550 vitamin K deficiency. 170 00:10:41.550 --> 00:10:44.550 Very high levels of the anticoagulant heparin. 171 00:10:44.833 --> 00:10:48.366 We've already mentioned the rare scenario of lupus anticoagulant 172 00:10:48.366 --> 00:10:53.433 with hypo program anemia, which can prolong both PD and PTT, 173 00:10:54.100 --> 00:10:57.783 and then pre analytic variables, something that we've seen, 174 00:10:58.633 --> 00:11:02.950 in recent months in our laboratory are some unusual patterns 175 00:11:02.950 --> 00:11:07.383 of interference in clotting times due to high levels of monoclonal protein 176 00:11:07.633 --> 00:11:11.883 that can cause sort of unpredictable patterns of clotting time prolongation. 177 00:11:11.883 --> 00:11:15.183 So that's another thing to think about, particularly if you're working 178 00:11:15.183 --> 00:11:19.000 with a population of cancer patients that may have B-cell lymphoma 179 00:11:19.116 --> 00:11:23.466 or plasma cell neoplasms generating high levels of monoclonal proteins.